Activity Report

Department of Mechanics
Royal Institute of Technology

July 1995-December 1996



This report was compiled from many bits and pieces of information. Thanks are due to all contributors. It reflects the activities of the fourth budget year (which was 18 months long) of the new department of mechanics in education, research and other areas. The manuscript was prepared by A. Burden, A. Dahlkild, P. Ekstrand, H. Essén, J Gunnarsson, A Johansson, E Lindborg, N Tillmark, I Wester and P Wikström.


Stockholm, May 1997

Arne Johansson, department chairman
Martin Lesser, department vice chairman


Table of Contents

1. Introduction
2. Personnel
3. Laboratory facilities, computers
4. Economy
5. Teaching activities
 5.1. Undergraduate courses
 5.2. Graduate courses
 5.3. Master theses ('examensarbeten')
 5.4. Awards
 5.5. Other Activities  
6. Research areas - short project descriptions
 6.1. Theoretical and applied mechanics
 6.2. Fluid mechanics
 6.3. Education Didactics
7. Research activities
 7.1. Doctoral theses
 7.2. Licentiate theses
 7.3. Conferences
 7.4. Publications 1995-
 7.5. Seminars
 7.6. Presentation
 7.7. Visiting scientists
 7.8. Visits abroad by staff
8. Other activities
9. The Faxén Laboratory
 9.1. Introduction
 9.2. Management and organization of the Centre
 9.3. Research performed at Faxén Laboratory
 9.4. Economics
 9.5. Personnel
 9.6. Miscellaneous


1 Introduction

This is the fourth annual activity report of the new mechanics department and because of the change in budget periods, it covers the period July 1, 1995 -- December 31, 1996. The mechanics department (web address: has approximately 75 employees and a yearly turnaround of nearly 40 MSEK. It is also host department for the Faxén Laboratory, a NUTEK competence centre for the fluid dynamics of industrial processes.

The head of department (`prefekt') is professor Arne Johansson and vice (`proprefekt') is professor Martin Lesser (Professor Henrik Alfredsson was vice chairman until Oct. 30, 1995). The study rector (`studierektor') is Hanno Essén.

The department board consists of, Henrik Alfredsson, Fritz Bark, Hanno Essén, Arne Johansson (chairman), Lillemor Lindbom, Anders Nilsson (prof. of technical acoustics, external board member), Daniel Söderberg (grad. stud. repr.), Lars Thor and an undergraduate student representative.

The teaching activities comprise courses in basic mechanics at all parts of KTH except the Schools of Architecture and Surveying, and a large number of higher level and graduate courses on many different aspects of mechanics of solids as well as of fluids.

The research activities can essentially be classified into two major areas, ``Fluid mechanics" and ``Theoretical and applied mechanics". There are altogether 36 graduate students active at the department (11 of which are associated with the Faxén Laboratory) and nine external graduate students in industry and research institutes. Two doctoral degrees and three licentiate degrees were awarded during the period July 1995 -- December 1996.

The Mechanics department together with fluid dynamics researchers at other KTH departments and at FFA earlier received the status of Swedish ERCOFTAC Pilot Centre (coordinator: Dan Henningson). A number of new partners from the different Nordic countries have now joined the centre, which now has received the status as Nordic ERCOFTAC Pilot Centre.

The Faxén Laboratory was formally started July 1995 and is directed by Professor Fritz Bark. The centre comprises activities at four different KTH departments (`Kemiteknik', `Materialens Processteknologi', `Mekanik', `Pappers- och Massateknik') and 13 industrial partners. The activities is divided into four program areas:

Altogether 15 doctoral students are are active in the program activities (for details see section 9).

Bengt Enflo was awarded the title of `Biträdande professor' (fall 1996).

12 new graduate students started during the 18 month period.

Marie Eriksson started in January 1996 as administrative assistent.

Helena Carlsson transferred to another position at Dept of Architecture, KTH, January 1, 1996.

Catrin Engelstrand started in May 1996 as administrative assistent.

Eric Rougier ended his position at the department May 31 when he reached the retirement age of 65.

Lars Bjernerstam started as department technician in Sept. 1996.

Pär Ekstrand started on a position to be responsible for the department's computers (Sept. 1996).

Dr Barbro M. Klingmann started as research associate (`forskarassistent') in December 1996.

Department meetings and miscellaneous

The department board met on September 20, 1995, February 13, 1996, May 29, 1996, October 28, 1996.

QCOM{176 } Teacher staff meetings were held on August 31, October 5, February 9, March 9, April 5 and May 11, where issues regarding mostly the basic mechanics courses were discussed.

A department meeting with Christmas dinner was held December 16-17, 1996 at the Häringe Castle.

A `samverkansgrupp' consisting of Arne Johansson (chairman) and Ingunn Wester as representatives for the employer, and three representatives for the employee organizations, Marcus Gallstedt (SF), Lillemor Lindbom (ATF) and Anders Thor (SACO) has been active. The tasks include, MBL negotiations.

A Christmas lunch was held on December 12, 1995 at the Restaurant Hasselbacken.

The department has a contract one hour per week at 'KTH-hallen' for `innebandy' or volleyball.


2 Personnel

This section is missing, please follow this link for the present staff.


3 Laboratory facilities, computers

The department has a laboratory with several permanent experimental facilities and advanced measurement equipment. A major experimental facility is the MTL wind-tunnel, which is a low-turbulence wind-tunnel with outstanding flow quality. It has a 7 m long (1.2 m x 0.8 m) test section and a maximum speed of 69 m/s. The turbulence level is as low as 0.02 %. It is used for a variety of long-term research projects on turbulence and laminar-turbulent transition. Among other major facilities we may mention:
- A shock tube for student laboratory exercises

- A subsonic wind-tunnel, 0.4 m x 0.5 m test section, max. speed 50 m/s.

There are also a number of smaller experimental apparatuses for research and student demonstration purposes:

- A rotating plane Couette flow apparatus and a curved rotating channel flow apparatus for studies of instabilities due to centrifugal and rot. effects.

- A plane Poiseuille flow apparatus (2m tex2html_wrap_inline10 1 m) for transition studies.

- A small water table for student demonstrations.

- A Hele-Shaw cell and Taylor-Couette apparatus.

- A small, flexible, low-speed wind-tunnel is under construction.

- The department also has access to a small supersonic wind-tunnel, 0.1m x 0.1m test section, at the department of Energy Technology.

The measurement systems include:

- Hot-wire anemometers.

- Two Laser-Doppler Velocimetry systems.

- Schlieren system with possibility for short duration double flash exposure.

Hot-wire anemometry is used extensively and many different types of probes are designed and made 'in-house'. The smallest wires used have a diameter of 0.6 tex2html_wrap_inline18 m and a typical length of 0.1 mm. A LDV systems was acquired during 92/93 and is a two-component fiber-optic system from Aerometrics using FFT technique. During 1997 the department will also be provided with a small single component fiber-optic LDV system for students lab work and an advanced particle image velocimetry (PIV) system based on pulsed laser and double exposure CCD camera. Data sampling is carried out mainly with Macintosh based systems.

This year a new UNIX based computer system has been set up managed by the department. Pär Ekstrand ( is responsible for the computers. The department has a computer system consisting of 27 SUN workstations, 12 IBM-RS6000 workstations, 8 X-terminals, (>)40 Macintosh computers and a number of PC's.

The system is mainly managed by three servers. A SUN sparc 4 called eiger for central services like mail, printers and DNS. As a part of the new system a new AFS cell and a Kerberos realm have been set up. There is 36 GB of disk storage in the AFS filesystem distributed on four 9GB disks with separate wide SCSI controlers for each disk. The disks are placed on two dedicated AFS file servers, a SUN sparc 10 called pollux and a SUN sparc 20 called castor. Both fileservers are dual processor machines. There is an aditional dedicated WWW and FTP server, a SUN Spark ? called nadelhorn.

A PC has been set up as a small modem service with four modems currently connected.

The department has four IBM-RS6000 workstations serving as numbercrushers, a model 590, a model 390, a model 375 and a model 370. They are setup in a DQS batch system. They where acquired 93-95 with grants from the Göran Gustafsson Foundation.

There is also two SUN Ultra2's, called dom and ask, shared by the department for interactive jobs.

A significant amount of computer time has also been granted to some of the research groups within the department from international supercomputer centers.

The department has signed a license agreement for Microsoft software as a part of a central agreement between KTH and Microsoft. It implies that we will have a continuous supply of upgrades, new versions etc of, e.g. Word and Excel. Also manuals will be supplied through this agreement (contact person: Lars Thor). The department also has licenses for a number of other softwares products.



4 Economy

A brief overview of the different categories of incoming resources to the department is given below for the period July 1995 - December 1996. The incoming resources to the Faxén Laboratory are not included here. These amount to roughly 10 MSEK per year (or 15 MSEK for the 18 month period). The Faxén Laboratory is described separately in section 9.

Dept. total
Education (GRU) 11.3 (12.5)
Research (FOFU) 13.0 (12.6)
External 17.3 (17.7)

Sum 41.6 (42.8)


The external funding is mainly composed of grants from TFR, NUTEK, The Göran Gustafsson Foundation and NFR. The numbers given within parenthesis correspond to 1.5 times the the values for 94/95, to enable a comparison with the previous budget year.

5 Teaching activities


5.1 Undergraduate courses

The course structure has remained stable for a couple of years now. Some teachers participated in a project to adapt the textbook by McGill and King to international standard notation etc. That project was, however, discontinued and as a result the schools that previously used McGill and King changed to the textbook by Meriam and Kraige. The old textbook by Thor-Höglund that is used in the schools E and B has been given modern typography.

Several teachers meetings were held and pedagogical methods and problems were discussed. Mandatory home assignment problems are now included as part of the requirements for almost all of the courses. The performance of the students vary a lot but the home assignments ensure that the students work continuously during the course.

The basic course in mechanics was also given as a summer course.

A project to develop a new basic course in mechanics was given resources (300 kSEK) from the 'prioriterade satsningar' internal KTH funds. The course will make extensive use of computer algebra.

The following is a list of undergraduate courses given during 95/96, here given with Swedish names (english translations given within parenthesis).

Grundkurser (basic courses)

Högre kurser (advanced courses)

5.2 Graduate courses

Fluid dynamics courses:
The courses Boundary Layers and Thermal Convection in Fluid Mechanics ( G. Amberg, D. Henningson and A. Johansson), Experimental methods in fluid mechanics (H. Alfredsson and A. Johansson), Numerical Methods in Fluid Mechanics (L. Fuchs) and Turbulence (A. Burden and A. Johansson) were also given with extensions as graduate courses (course numbers: 5C5118 5 p, 5C5039 5 p, 5C5114 5 p and 5C5112 6 p, respectively).

- Fluid Mechanics, Advanced Course (5C5105 10 p) was given by G. Amberg, A. Dahlkild and M. Hallbäck.

- Fluid Mechanics for Graduate Students, Continued Course (5C5120 3 p)

Theoretical and applied mechanics courses:
- Modern analytical mechanics (5C5001 8 p) was given by M. Lesser
- Relativistic mechanics (5C5003 3 p) was given by B. Enflo
- Introduction to relativistic continuum mechanics (5C5117 3 p) was given by L. Söderholm
- Infinite dimensional dynamical systems (5C5123 4 p) was given by H. Dankowicz
- Non-linear oscillations and dynamical systems (5C5045 5 p) was given by A. Nordmark
- Foundations of classical mechanics (5C5046 5 p) was given by P. Dahlqvist and K.-E. Thylwe


5.3 Master theses ('examensarbeten')

Advisors are given within parenthesis.

950725 Lavalley, Renaud, Direct Numerical Simulation of Homogenous Isotropic Turbulence Focused on Passive Scalars (A. Burden).

951130 Wedin, Ruben, Evaluation of the CFD Program STAR CD Application to a Vortex Pump (G. Amberg).

950811 Windecker, Ulrike, Design of a Device for Calibration of Hot-Film Sensors at Low Velocities in Air (H. Alfredsson).

950830 Winkler, Christian, Prandtl Number Dependence of Stability of Convection in Floatzones (G. Amberg).

951006 Mimer, Markus and Sunvisson, Emil, Survey of a Single Jet Fluidic Oscillator Feedback Loop (R. Lindgren).

951208 Borglund, Dan, On the Search for Optimal Trajectories to the Moon, TRITA-MEK 95-14 (H. Essén).

960130 Axelsson, Emil, Simulation of the Flow in the Diffusing Elements of a Propeller Pump (G. Amberg).

960312 Reinson, Viktoria, A Method for Simplified Simulation of Polydispersed Settling (G. Amberg).

960329 Audenis, Gérald, Potential Flow through Contractions of Slowly Varying Radius (A. Dahlkild).

960329 Ingare, Olof, and Rylander, Anders, Development and Implementation of a Dead Reckoning Navigation System for an Autonomous Vehicle (R. Lindgren).

960419 Larsson, Roger, Interactive Visualisation of Flowfield Data A. Dahlkild

960521 Halvorsen, Alf Kjartan, A Kinematic Model of the Foot, TRITA-MEK 96-3 (M. Lesser).

960529 Moreno, Patricia, CFD Analysis of an Experimental Plug Nozzle (H. Alfredsson).

960627 Franzmann, Dirk, By-Pass Transition Modelling Based on an Extended Single-Point Closure, TRITA-MEK 96-4 (M. Hallbäck).

960808 Colling, Richard, Shape Optimization of a Nozzle Solution of the Adjoint Euler Equations for Quasi-One-Dimensional Flow (H. Alfredsson).

960822 Östman, Anders, Numerical Simulation of the Flow in a Waterjet Intake (L. Fuchs).

960901 Johansson, Lise-Lotte, The surface tension and its temperature dependence - an experimental technique, TRITA-MEK 96-6 (H. Alfredsson/ G. Amberg).

960902 Sundell, Johan, Fluid Mechanical Aspects of Cooling of Rectifier Cabinets (G. Amberg).

961003 Odelram, Johan, Experimentella studier av vätske-vätske separering (F. Bark).

961125 Eriksson, Lars, Simuleringsprogram för kvasistationär strömning i en krutmotor (A. Dahlkild).

961212 Högberg, Markus, Cross-flow vortices and their secondary instability in Falkner-Skan-Cooke boundary layers (D. Henningson).


5.4 Awards

L. Thor was awarded the annual teacher of year prize for the academic year of 95/96 by the students at the School of Mechanical Engineering, KTH.

N. Apazidis was awarded the annual teacher of year prize for the academic year of 96/97 by the students at the School of Technical Physics, KTH.

M. Hallbäck was awarded the annual teacher of year prize for the academic year of 96/97 by the students at the School of Industrial economy.



6 Research areas - short project descriptions

Short descriptions of on-going research projects are given below. The publication numbers refer to section 7.5.



6.1 Theoretical and applied mechanics

Shock wave propagation in fluids

Researchers: Nicholas Apazidis, Martin Lesser, Graduate student: Bo Johansson

Sponsors: TFR.

This project deals with propagation of shock waves in liquids and liquid impact problems. Generation, reflection and convergence of shock waves in confined chambers of various forms is investigated on the basis of Whitham's non-linear theory of geometrical shock dynamics. This theory has been extended by a new theoretical and computational method, developed by Apazidis & Lesser (1996). The method can be applied to the propagation of shocks arbitrary in strength and form into a medium with no-homogeneous flow conditions.

Calculations based on the new approach have been applied to the problems of shock reflection and convergence in various types of confined chambers. It is shown that by an appropriate choice of the form of the reflector boundary one may obtain reflected shock waves having desirable shapes, for example a near-square shape. Also reflectors with parabolic geometry are considered. A cylindrical wave is generated at the focus of the parabolic cross-section. It is shown that contrary to the linear case the reflected wave is no longer planar. Experimental investigations of shock focusing in a thin confined chamber with a reflector boundary in the form of a slightly perturbed circle have been carried out. Experimental results confirm the possibility of producing polygonally-shaped converging shocks.

Technological and medical applications of the project may be found within the fields of shock wave propagation, shock induced collapse of cavities, erosion, disintegration of kidney and bladder stones by means of a shock wave attenuation in lithotriptor devices.

Publications: 1,37,100,101

Chaotic systems and their quantization

Researchers: Per Dahlqvist

Sponsor: NFR

Chaotic systems and their quantum counterparts are studied. Classical and semiclassical properties are studied in a unified formalism involving concepts such as dynamical zeta functions, evolution operators and periodic orbits. The emphasis is on bound systems exhibiting intermittency. Classically, computation of properties like Lyapunov exponents, decay of correlations and diffusion rates are considered. Semiclassically, the accuracy of quantization schemes for chaos and the limitations of suggested universal properties are studied.

Publications: 6,7,8,9,10,11,12

Dynamics of Hamiltonian systems with applications to celestial mechanics

Researcher: Harry Dankowicz

Sponsor: The Göran Gustafsson Foundation

The geometry of certain higher-degree-of-freedom Hamiltonian systems allows for a perturbation approach to the study of stochasticity and chaotic behavior, such as sensitive dependence on initial conditions and diffusion in phase space. In particular, the motion of small grains in the vicinity of asteroids and the rings of the greater planets falls into this category. We study the global structure of phase space and obtain measures for characteristic escape rates of the grains from the asteroids.

Publications: 13,14,15,16,17

Dynamical models of friction

Researcher: Harry Dankowicz

Sponsors: The Göran Gustafsson Foundation, TFR

We develop models of friction which incorporate dynamical, inertial type effects as well as history dependency, such as hysteresis. These are simulated for comparison with actual experiments. We aim to simplify these models to low-dimensional systems which could be more easily simulated and, hence, used in control contexts etc.

Propagation of nonlinear acoustic waves and beams

Researchers: Bengt Enflo, Claes Hedberg

Sponsor: TFR

In the project basic problems of nonlinear acoustic wave propagation are studied. Burgers' equation and its generalizations are studied by analytical and numerical methods. Applications are found to propagation of shocks and signals in the sea and in the atmosphere. Examples of problems studied by use of equations of Burgers' type are: finding asymptotic waveforms originating from spherical and cylindrical sine waves and short pulses, nonlinear acoustic wave propagation in dispersive and layered media and design of effective shock pulses in sound beams.

Publications: 18,19,29,75,76

Theoretical investigations of underwater sound

Researchers: Bengt Enflo, Graduate student: Henrik Sandqvist

Sponsor: TFR

The project is to study theoretically the propagation of underwater sound under conditions similar to those occurring in realistic applications. That means that refraction and the stratification of the medium are taken into account. Nonlinear effects are taken into account: low frequency narrow beams are assumed to be produced by nonlinear interaction of fundamental monochromatic waves (so called parametric radiators). Attempts are made to find, numerically and analytically, solutions of generalizations of Burgers' equation, which describe sound beams in dispersive and inhomogeneous media.

Diffraction of sound by noise barriers

Researchers: Bengt Enflo, Graduate student: Ivan Pavlov

Sponsors: BFR, KFB

Noise from traffic, fans, motors etc. is often shielded by barriers. In normal design the top edge of a noise barrier is straight. The edge may act as a string of highly correlated point sources. The effectiveness of the barrier is reduced by the coherence of these secondary sources. Experiments at The University of Texas show that the effectiveness of the barrier can be increased if it is made irregular. The project aims at understanding of these phenomena by theoretical methods. It will continue with theoretical and experimental investigations of possibilities of increasing the effect of sound barriers.

Theoretical acoustical investigations with applications in musical acoustics Researcher: Christer Nyberg

Sponsor: LUFT

The purpose of this project is to investigate nonlinear generation of combination frequencies in cavities. The tone generation in musical instruments is often described in terms of a clearly defined nonlinear element which can excite the rest of the instrument, treated as a linear, passive, multimode cavity. However, linear theory, which requires small amplitudes, seems to be inadequate for describing the sound field in a cavity close to a resonance, as finite amplitudes are predicted even with dissipative effects included. If the sound field is excited by two frequencies close to resonance, nonlinear interaction is therefore expected to become important. Starting with a nonlinear generalization of d'Alembert's wave equation together with appropriate boundary conditions, the acoustic wave field in the cavity is calculated and can then, in the case of periodicity, be decomposed into its Fourier-components.

Publications: 43,44

Dynamical systems and multi-body modelling Researchers: Martin Lesser, Hanno Essén, Arne Nordmark, Graduate Students: Mats Fredriksson, Anders Lennartsson

Sponsor: TFR, LUFT

The purpose of this study is to integrate modern methods of modelling multi-body systems with recent results in the theory of dynamical systems. Thus far most dynamical systems treated under the new heading of chaos theory has involved concentration on very low degree of freedom models derived in a somewhat ad-hoc fashion as representations of more complex mechanisms. Our aim is to combine our new techniques for dealing with complex mechanisms by computer algebra and Kanes equations with the methods of dynamical systems theory to achieve useful and readily interpretable representations, e.g. by means of center manifold ideas. One particular area of interest is problems of impact in subassemblies of complex mechanisms.

Publications: 21,23,25,36,64,87,110

Mechanics of The Vasa Steering System

Researchers: Martin Lesser, Graduate Students: Anders Lennartsson, Jesper Adolfsson. Examine Worker: Gustaf Eriksson, Cooperative Researchers: Dr. Thomas Wright, Science Museum, London

Sponsor: Internal Funds

The steering mechanism of the Vasa, known as a "whipstaff" was of the type used in ships for a thousand years. It is the only surviving example of this device which for the most part has gone undocumented. A number of issues concerning the way the mechanism has been reconstructed, how it was used and the possible problems of physical damage to the steersman in carrying out his task are at issue. The project, in cooperation with the Vasa Museum and the Science Museum in London is designed to answer these questions. As part of the work we are preparing a simulation of the mechanism which will be placed in the Vasa museum. The simulation is partly an actual copy and partly a servo steered mechanism run by a computer program. Users will get some of the sense of what was involved in steering the ship.

A paper on the project will be presented at the 3rd Euromech Solid Mechanics Conference to be held in Stockholm in August 1997.

Figure 1: A computer simulation of the Vasa's steering mechanism and its interaction with the steersman's arm. Recovered bones from the steersman show damage of a type that may be due to aspects of his work with the whipstaff (the section of the steering mechanism which was manipulated by the steersman). The inset shows a model of how the steersman and crew may have looked during the period. The Vasa's whipstaff mechanism is the only fully recovered example of a device which was used in European ships for over 1000 years.

Design of complex mechanical systems Researchers: Martin Lesser, Sören Andersson (Machine Elements), Lennart Karlsson (Computer Aided Design, Luleå), Tore Risch, (Computer Science Linköping), Volvo Corporation. Graduate student at KTH: Claes Tissel

Sponsor: NUTEK

Complex mechanical systems are treated by a combination of modern methods for simulation, computer aided design tools and object oriented data base technology. The aim of the project is to assemble all of these techniques into a usable design tool. Several particular problems are being used as test cases. These include blade mountings in jet engines and exhaust manifold in automobiles.

The Mechanics of Overhead Railroad Electrification Systems

Researchers: Martin Lesser, Anders Lennartsson, Gitte Ekdahl Cooperation with: Professor Lennart Karlsson, Division of Computer Aided Design, LUT

Sponsors: Swedish State Rail Authority, Banverket.

This is an experimental, theoretical and numerical study of the overhead electrification system used in high speed trains. Both the pantagraph mechanism, which sits on the roof of the train and the overhead cabel system are treated. The purpose of the project is to determine what are possible damage mechanisms to the device, what are the speed limits set by it and what criteria may be used in evaluating possible interactions of new type pantagraphs with the Swedish rail systems power lines.

A paper on the project will be given at the third Euromech Solid Mechanics Conference.

Continuum equations for moderately rarefied gases

Researchers: Lars Söderholm, Naoki Yoshida.

Sponsor: LUFT, TFR

For moderately rarefied gases the Navier-Stokes equations do not apply. Neither can, in practice, the Boltzmann equation be used directly. The Burnett equations fit into this gap. They are, however, beset with many difficulties like instability for short wavelengths, unknown boundary conditions and thermodynamic inconsistency. For Reynolds numbers of the order unity, the difficulties have been overcome (Sone). The stability problem has recently been overcome (Zhong et al.) for arbitrary Reynolds numbers. As a first step in a different approach, an approximate solution to Boltzmann's equation in terms of 13 moments has been obtained. It is exact to first order in the mean free path (containing the Navier-Stokes equations with the full viscosity as a limit) . Its thermodynamic properties are being studied. A comparison with ultrasound data is made. Basic properties of the Burnett equations are also being studied.

Non-linear waves and integrability

Researcher: Lars Söderholm.

Sponsor: LUFT.

An important class of non-linear wave equations turns out to be completely integrable. Most of these equations are weakly non-linear approximations to non- linear equations such as the Korteweg-de Vries equation and the non-linear Schrödinger equation (valid for long and short water waves, respectively). The fully non-linear field equations of general relativity are, however, exactly integrable when sufficient symmetry give just two independent variables. Integrable equations can be considered intrinsically linear as they via (non-local) transformations can be reduced to linear equations. This calls for an intrinsic, geometric description. In general relativity such methods have been employed for a long time. The field equations of general relativity are studied for the axially symmetric case. Some of these questions are pursued in cooperation with Michael Bradley, University of Umeå.

Time-Dependent Normal Form Hamiltonian

Researchers: K.-E. Thylwe, in collaboration with H. Dankowicz.

Sponsor: 'Rörlig resurs, KTH'.

The research focuses on the development and application of a new normal form for physically relevant time-dependent Hamiltonian systems. This theory is of significance in various physical contexts: - In semiclassical quantization of mixed chaotic model systems with soft potentials; - In certain simplified models of electromagnetic wave propagation where the nonlinear Schrödinger equation plays a central role; - In other situations such as pattern formation and instabilities in infinite dimensional systems; the relevant class of equations appear in searching for stationary solutions of non-homogeneous, dissipative partial differential equations;

The TD normal form is also an elegant framework for obtaining adiabatic approximations, i.e. assuming slow variations in the coefficients, in the above applications.

Publications: 26,31,32,33,54,55,56,57,85



6.2 Fluid mechanics

Experiments on stability, transition, separation and turbulence in boundary layer flows

Researchers: Henrik Alfredsson, Andrey Bakchinov, Per Elofsson, Carl Häggmark, Mitsuyoshi Kawakami, Masaharu Matsubara, Nils Tillmark, Johan Westin

Sponsors: NUTEK, TFR, KVA, Göran Gustafsson stiftelse

The receptivity of the laminar boundary layer to free stream turbulence is investigated through detailed velocity measurements in the MTL wind tunnel, where free stream turbulence is generated by different grids. Both flow visualisation and hot-wire measurements (one and two-point) have shown that the interaction with the boundary layer gives rise to elongated structures of high and low velocity. These streaks seem to be susceptible to secondary instabilities and subsequent breakdown. This interaction is presently studied.

Formation of elongated structures may also occur through the interaction between two finite-amplitude oblique waves. This is experimentally investigated by introducing two oblique TS-waves in an air flow channel by means of vibrating ribbons (one at each channel wall). Measurements were carried out at Reynolds numbers of about one third of the critical one, and at an initial streamwise disturbance level of the order of 1-4 %. With only one ribbon excited the oblique wave decayed downstream in accordance with linear theory, but with the excitation of both ribbons dramatic changes of the flow field occurred. A strong mean flow distortion in the form of a spanwise peak-valley structure and a strong growth of higher harmonics prior to breakdown were observed. In a new series of experiments streaks are formed through regularly spaced suction holes. If the streaks are strong enough naturally secondary instability develops and the flow breaks down to turbulence. Secondary instability of the streaks is also studied by introducing controlled disturbances.

The oblique transition scenario has also been investigated in a laminar boundary layer in the MTL-wind tunnel where the waves have been generated through a spanwise slot connected to up to six different loudspeakers. Also here good agreement with the transient growths scenario has been obtained. These measurements are still analysed.

Another study deals with separation of a laminar boundary layer on a flat plate subjected to an adverse pressure gradient. The pressure gradient is imposed by an adjustable bump mounted at the upper wall, forcing separation at the plate. The boundary layer on the upper wall could be controlled by suction from a porous section of the bump. Hot-wire measurements and flow visualizations showed that the front part of the separation bubble induced on the plate was 2D and steady whereas in the reattachment region an unsteady 3D vortical shedding motion appeared. Flow visualizations further revealed a spanwise periodicity of these vortices. So far experiments on the response of the bubble to the natural wind tunnel disturbances (low level disturbances), controlled disturbances in form of TS-waves as well as grid generated free stream turbulence (FST, level 1.5 %) have been studied. Under low disturbance conditions natural wave packets are detected in the separated shear layer of the bubble. Frequency spectra from the shear layer show a quite distinct peak from the wave packets indicating that there is a strong wave frequency selection in the shear layer. These waves can be studied in more detail by introducing two-dimensional deterministic waves upstream of the separated region. The waves are generated upstream of the adverse pressure gradient by suction and blowing through a slot at the leading edge. In the negative pressure gradient boundary layer upstream of the bubble the TS-waves are damped while in the separation region they are strongly amplified (several orders of magnitude). The influence of excitation amplitude and frequency of the waves on the mean flow has been investigated.

FST was found to have a significant effect on the structure of the separation bubble and reduced the size of the separated region. The disturbance growth was found to be exponential in the TS-case and linear in the FST-case, but seemed to saturate at the same level in both cases. A related study of numerical simulations of separated flows is carried out by Prof. Henningson.

In cases where body forces affect boundary layer flows different other types of instability may be dominating. For instance a boundary layer flow along a wall in a rotating system will be affected by a Coriolis force which can give rise to instabilities in the form of longitudinal vortices. Similar vortices can develop along concave walls due to centrifugal effects. These instabilities may arise at much lower Reynolds numbers than the traditional TS-wave instability. The enhanced heat transfer of such vortices as well as secondary instability are studied through controlled experiments in an air channel with system rotation. Both temperature and velocity measurements are made with hot-wire technique.

For plane Couette flow with system rotation, the Coriolis force will either be stabilizing or destabilizing across the full channel width. Linear stability theory shows that the critical Reynolds number is as low as 20.65. Our experiments have verified the linear theory and also shown that the flow exhibit a number of interesting secondary instabilities which occur on top of the primary roll cell structure. The experiments show furthermore that rotating plane Couette flow exhibits a rich variety of flow phenomena, some of which has not been observed in other flow situations, such as relaminarization for stabilizing rotation.

Publications: 5,42,58,67,70,74,86,94,95,115,118

Control of low-dimensional models of the turbulent boundary layer

Researchers: Harry Dankowicz, Brian Coller (California Institute of Technology)

Sponsor: The Göran Gustafsson Foundation

We study low-dimensional models of the turbulent flow in boundary layers. in particular, we apply the evolutionary algorithm known as Genetic Programming to finding suitable control strategies for the suppression of burst-type behavior in the models. These bursts are thought to be essential in the production of turbulence in the main flow

Boundary layer transition - Theory and DNS

Researchers: Dan Henningson, Stellan Berlin, Casper Hildings, Anders Lundbladh


This project involves research to determine the maximum growth possible of disturbances evolving according to linear theory, as well as to investigate the importance of this growth when non-linearity comes into play. Several shear flow types have been considered. The results show that non-modal growth, i.e. growth not associated with individual eigenmodes but inherently dependent on their superposition, can cause large transient amplification. This growth is mainly associated with streaky structures in the streamwise direction. Non-linear calculations have shown that when the optimal disturbances from linear theory are used as initial conditions, the threshold amplitudes required for transition to turbulence is lower than for general disturbances.

Another part of the project involves direct numerical simulations (DNS) of transition to turbulence where these transient growth mechanisms play a major role. This bypass of the traditional Tollmien-Schlichting instability waves is involved in many shear flow transition scenarios. Previously transition associated with localized disturbances have been investigated, and at present the transition in boundary layers starting with a pair of oblique waves is investigated. These waves generate elongated structures in the streamwise velocity which rapidly grow due to the non-modal mechanism.

Finally transition in flows with separation is considered. Here DNS of a laminar separation bubble is investigated and disturbances added in order to study laminar separation and turbulent reattachment.

Publications: 30,46,72,80,81,90,91,106,107,111

Active Control of Boundary-Layer Transition

Researchers: Markus Hogberg, Martin Berggren, Dan Henningson

Sponsors: TFR, HPDR, FFA

Study and design of active control strategies for transition in boundary layer flows is done within this project. The control strategies will are designed using the optimal-control approach to control of the Navier-Stokes equations and the adjoint-equation technique for associated gradient computations. The strategies will be designed to control or delay bypass transition. This represents a significant new step compared to previous work almost exclusively devoted to anti-phase modal suppression of two-dimensional TS-waves or wave packets. In particular the aim is to control the growth of streaky structures associated with most bypass transition scenarios. The application is flows with free-stream turbulence, where an optimally designed feed-forward control will be implemented experimentally to delay transition.

Modern stability prediction methods

Researchers: Paul Andersson, Ardeshir Hanifi, Dan Henningson

Sponsors: NUTEK, ESA, FFA

The project concerns a new transition prediction tool which is being developed in cooperation with DLR in Gottingen. The code uses the parabolized stability equations (PSE) and is so far based on the linearized equations. The method uses a wave ansatz with a slowly varying amplitude function and wave number, similar to the WKB method. In addition an auxiliary condition is introduced which ensures uniqueness of the solution so that the traditional WKB expansion can be avoided. This method has proven to be efficient and to produce accurate stability results for complicated flows. It has been carefully checked against existing solutions and will be extended to handle non-linear interactions between wave components.

Applications motivating the development of this method is the hypersonic transition research carried out within the ESA FESTIP program and laminar wing design carried out in the CEC EUROTRANS program.

Publications: 28,63,68

Calibration and development of turbulence models

Researchers: Martin Skote, Dan Henningson

Sponsors: NUTEK

Correct modeling of turbulence is one of the most crucial areas for design computation of flow around wings and aircraft configurations.

Current models are not accurate enough for many common flow cases, especially when they contain zones of separated flow. The progress towards more reliable turbulence models is considerably slowed down by the problems of calibration of these more complex models and by the numerical problems they induce, in particular close to solid surfaces.

While most of the current model calibration relies on experiments, the advent of faster computers now allows simulation of turbulent flow at increasing Reynolds numbers. From simulated data each term in the exact model equation can be computed individually and the model calibrated term by term.

High quality simulation data applicable to calibration is at present scarce. This is especially true for the aeronautically important cases of three-dimensional and separated boundary layers.

In the project we simulate turbulent boundary layers for a number of flow cases including adverse pressure gradient and separated flow with parameters in the range of interest for aeronautical applications. From the simulated data, turbulence models in current use for aerodynamic design are validated and/or calibrated. The problems associated with more advanced turbulence models in the near wall region are also considered.

Modelling of solidification in materials processing

Researchers: Gustav Amberg, Robert Tönhardt

Sponsors: TFR, KTH (rörlig resurs).

During solidification, for example in casting or welding, mushy zones consisting of dendritic crystals often form. The properties of a finished casting are determined by the size and morphology of the crystals, and is often strongly affected by convective heat and mass transfer during solidification. This project is concerned with mathematical models for solidification in processes such as welding and near net shape casting. One part of this is to predict microstructure, i.e. the crystal structure and the size, geometry and orientation of crystals. The models developed within the project are to be incorporated in available codes for simulating the macroscopic convective heat and mass transfer during solidification. Development of mathematical models will require simulations of individual dendrites. Models and predictions will be continuously tested against experiments (in collaboration with Hasse Fredriksson, KTH).

Another issue which is studied is the rather complex dynamics of convective flow through the mushy layer, giving rise to well known defects such as macrosegregation and freckles. Such specific phenomena has been studied within this project and will be investigated further, using the code and models that are developed. During the work described above, symbolic code generation tools ( gustava/femLego) have been used to a large extent.

Figure 2: An initially small nucleus of a pure metal has involved into a large crystal. The crystal is attached to a solid wall and grows away from the wall into an external shear flow of an undercooled melt (Pe=15,Pr=23). The innermost contour is the interface between the solid and liquid phase and the other contours are isotherms. Some of the effects of the flow is the tilt of the main branch and asymmetric the branch structure.

Thermocapillary convection in materials processing.

Researchers: Gustav Amberg, Henrik Alfredsson, Christian Winkler, Renaud Lavalley

Sponsors: TFR, KTH (rörlig resurs)

If surface tension depends on temperature, a fluid motion will be induced along a free surface with a temperature gradient. This is an important phenomenon in many materials processes, characterized by large temperature gradients, small volumes of liquid metal, and the presence of free surfaces. This convection is often crucial for the properties of the finished product. Examples of such processes are all the various techniques for crystal growth, and welding, where the flow in the weld pool determines the penetration of the liquid pool (i.e. 'weldability'). Often it is technically important to avoid oscillatory flow, and thus it is important to understand the stability characteristics of thermocapillary convection in general.

An experimental study of the transition from stationary to oscillatory motion in buoyant thermocapillary convection has been made. Instability was observed through flow visualization in quantitative agreement with numerical calculations. The emphasis is on identifying instability mechanisms, in conjunction with numerical simulations.

Welding of the light metals Aluminum and Titanium today presents a number of practical difficulties. The flow in the melt during welding of Al and Ti alloys will be studied by numerical simulation, using tools and models developed in accompanying projects. This will be closely coupled to an experimental study of Al and Ti welding carried out by Torbjörn Carlberg, Sundsvall.

Another process where thermocapillary convection is crucial is float zone crystal growth. The stability of the flow in such processes are simulated numerically and comparisons are made with actual float zone experiments in space and on earth (Torbjörn Carlberg, Sundsvall). During the work described above, symbolic code generation tools ( gustava/femLego) have been used to a large extent.

(Cooperation with Torbjörn Carlberg, Sundsvall, and Mårten Levenstam, CTH)

Publications: 38,39,99,109,113

Transport in electrochemical systems

Researchers: Fritz Bark, Shigeo Kimura*, Lars-Göran Sundström, Michael Vynnycky*

Sponsor: TFR

The purpose of this project is to provide the electrochemical industry with solutions to some fundamental problems whose understanding is of importance in the design of cells with a liquid electrolyte. In such cells, transport of ionic species is due to three different mechanisms - convection, migration (due to the electric field), and diffusion. Reaction kinetics enters as boundary conditions on the electrode surfaces. The work is at present undergoing a theoretical phase, with experiences from previous experiments as a valuable basis. Both steady and time-dependent situations with and without natural convection are treated. Morphological instabilities, which cause the (unwanted) formation of dendrites, have been investigated, and at present thermal and hydrodynamic instabilities are under consideration. Because of the analogy between heat and mass transfer, many of the results are directly applicable to heat transfer cases. As regards to multi-phase transport, some theoretical work on diffusion in porous electrodes and separators has been made and a paper is in preparation. In a longer perspective, effects of gas bubbles in the electrolyte will also be considered.

* Affiliated with the Tohoku National Industrial Research Institute, Agency of Industrial Science and Technology, Sendai, Japan.

Publications: 4,34,45,48,49,50,61,62,71,108,116,117

Fluid dynamics of plane liquid jets

Researchers: Henrik Alfredsson, Daniel Söderberg

Sponsors: NUTEK

In the paper making industry plane jets of a low concentration fiber suspension distributes the fibers to the paper machine. For a typical paper machine the jet width can be 10 m with a thickness of about 1 cm, and velocities of the order 10-30 m/s. The flow is ideally two-dimensional, however, paper is usually not perfectly homogeneous across its width, showing that the jet flow is not perfect. This can be due to inhomogeneities in the jet contraction, centrifugal instability in the form of Dean vortices or inhomogeneous break-up of the jet. For plane jets the surface is affected both by a surface tension force which always tends to restore the interface back to its original equilibrium position, whereas the aerodynamic forces developing at the interface between liquid and gas enhance the instability. This may cause the instability to grow until the liquid sheet disintegrates and splits up into droplets. The research program aims at increasing our knowledge about the development of two-dimensional liquid jets in air, both for Newtonian liquids (i.e. pure water) and fiber suspensions typical for paper making.

Figure 3: Streaky structures, observed through smoke visualization, in a laminar boundary layer at tex2html_wrap_inline281 2 m/s subjected to 6 % free stream turbulence. Flow is from left to right. White markers are 10 cm apart. Note sign of streak oscillations and breakdown at the downstream end of the photograph. From Alfredsson & Matsubara, (1996).

Sedimenting two-phase flow

Researchers: Anders Dahlkild

Sponsors: FaxénLaboratoriet

Problems of gravitational sedimentation of small particles suspended in a fluid are studied theoretically. A fundamental problem in separation processes is the removal of accumulated material of settled particles on the container walls. The models of shear induced resuspension of particles has been complemented to account also for Brownian diffusion of particles. In particular, the accumulation and flow of particles down an incline are studied. With Brownian diffusion included steady solutions are found in parameter regimes which otherwise would lead to a continuous packing of a very dense sediment. Additional extensions of the model includes a yield stress due to interparticle friction appearing at elevated concentrations.

Theoretical studies of the wave-number spectra of turbulence

Researchers: Erik Lindborg, Anthony Burden, Arne Johansson

Sponsors: TFR

This activity has been focused on theoretical and numerical analysis of the statistical formulation of turbulence in real space and in wave-number space. The kinematical theory of homogeneous axisymmetric turbulence has been given a simple and concise formulation, which has been successfully applied in the analysis of the experiments on axisymmetric turbulence by Torbjörn Sjögren. Kolmogorov's third order structure function law has been derived from an equation where the pressure terms and mean flow gradient terms are retained. A new inertial range law, relating the two-point pressure-velocity correlation to the single-point pressure-strain tensor, has been derived. This law shows that the two-point pressure-velocity correlation, just as the third order structure function, grows linearly with the separation distance in the inertial range. The project ended during 1996, when Erik Lindborg defended his doctoral thesis `Studies in classical turbulence theory'.

Publications: 40,41

Measurement, modelling and simulation of turbulence

Researchers: A.V. Johansson, M. Hallbäck, E. Lindborg, , K. Alvelius, T. Hambraeus, T. Sjögren, S. Wallin, P. Wikström

Sponsors: TFR, NUTEK, The Göran Gustafsson Foundation, KTH

The group's activities on turbulence modelling and simulation span the range from fundamental theory of isotropic and axisymmetric turbulence to development and testing of engineering turbulence models, as well as a number of direct and large-eddy simulation approaches. A main underlying theme has been the improvement of understanding of the many aspects involved in the development of single point closures of turbulence. Among recent major achievements of the group in the modelling area we may mention:

A general aim in our work has been, not only to develop new single-point turbulence models, but to improve the understanding of issues involved in such a development and inherent limitations at various levels of closures. Most such existing models do not satisfy basic kinematic constraints and conditions such as realizability. Requiring the models to satisfy such conditions is a powerful tool in the efforts to increase the generality of models. A crucial aspect has been the choice of rather highly idealized flow situations that allow a wide variety of approaches. Direct numerical simulations have been used extensively in the testing of models of specific terms in, e.g., the Reynolds stress transport equations. The simulation code has been developed into a general and flexible tool implemented on both serial and massively parallel computers, and adapted for homogeneous flows as well as for channel flow type of geometries. One doctoral project (K. Alvelius) has develeoped a large-eddy formulation of the code, and has used this type of computations for evaluating turbulence modelling quantities such as pressure strain rate at high Reynolds numbers. This has been quite successful and the achievements will be presented in a Lic. thesis on June 3, 1997.

The general tendency in our efforts is also to approach an increasing degree of complexity of the flows treated, including near-wall effects and other inhomogeneities. A new explicit Reynolds stress model has recently been developed (Wallin & Johansson 1997) that has been implemented in the FFA EURANUS code which is a versatile CFD code. The model has been tested in a number of flows, one of the most complicated case being a shock-induced separation zone in a Mach 5 turbulent boundary layer. It was demonstrated that the model is capable of capturing the skin friction variation as well as separation zone length variation with shock strength. The new EARSM model has also been applied to flows around stall-regulated wind turbine blades (Hambraeus).

Physical experiments are still of primary importance in this field and considerable efforts have been spent on development of techniques to measure the various terms in the Reynolds stress transport equations with high accuracy. For instance, for the dissipation rate tensor this involves measurement of velocity derivative moments. The MTL wind tunnel at KTH permits the study of homogeneous turbulent flows with quite high Reynolds numbers, more than an order of magnitude higher than what can be achieved by numerical simulations today. Many flows of practical and technical interest, such as turbulent boundary layers, channel flows, flows in nozzles etc, show a high degree of anisotropy in the Reynolds stress components. Also external force fields such as strong rotation may alter the turbulence characteristics significantly and cause a high degree of anisotropy. In anisotropic turbulence the pressure forces act to randomize the field, a process manifested by an intercomponent energy redistribution, the modelling of which is of crucial importance when predicting the turbulent flow field. Much of the work in the present project has been directed towards a better understanding of the intercomponent energy transfer processes, in particular their modelling in differential and algebraic Reynolds stress closures.

A particular strength of the turbulence group is the possibility of comparing and combining results obtained from theoretical analysis, experiments and direct numerical simulation. We have systematically taken advantage of the rapid increase in computer resources at PDC (at KTH). In a series of studies we have investigated in detail return-to-isotropy mechanisms in axisymmetric anisotropic turbulence relaxing towards isotropy and in the presence of finite strain. For the first time ever we have been able to determine separately the different parts of the pressure strain term in an experiment. This was made possible by a new theoretical development of Lindborg (1995) for the kinematics of axisymmetric turbulence. A new model for the rapid term was constructed (Johansson & Hallbäck 1994), which was shown to give a very good desciption of the data found in the experimental investigation. The experiments and further model developments were part of the doctoral thesis of Torbjörn Sjögren that was presented in April 1997. A part of the thesis also concerned the use of symbolic manipulation software for automated generation of codes for the testing of turbulence models. This was also combined with user-friendly interactive interfaces, and constitutes a platform for much promising future work.

Publications: 2,27,68,82,83,84,92,93,96,97

Numerical simulation of turbulent plane Couette and pipe flows

Researchers: Arne Johansson, Jukka Komminaho

Sponsors: KTH

Fully developed turbulence in plane Couette flow is studied by means of direct numerical simulation. Experience has shown that this is a particularly difficult case to study because of a tendency to develop extremely long vortical structures aligned in the streamwise direction. For a numerical simulation study an extremely long (and also rather wide) box is needed, almost 90 half-heights long in the present case. The computations were carried out on a massively parallel computer (CM200) at KTH where the calculations amounted to a total of about one CPU-month. Accurate statistics have been acquired and the long structures have been studied in detail. It was also shown that a weak (spanwise) rotation has a drastic effect on the long structures. Comparisons with experimental results of Tillmark & Alfredsson show excellent agreement (see Komminaho et al. 1996). Also the relaminarization of plane Couette flow turbulence was studied by a step-wise lowering of the Reynolds number. This was achieved by increasing the viscosity, thereby avoiding the instabilities that would occur if the velocity suddenly was decreased. The transition Reynolds number could hereby be determined to about 360 thereby substantiating the previous numerical/experimental findings of Lundbladh & Johansson and Tillmark & Alfredsson. Also the turbulence regeneration mechanisms could be elucidated at low Reynolds numbers. Strong similarities were found with the streak instability mechanisms observed in typical bypass transition scenarious in various flows. The results will be presented at an international conference in August 1997.

We have also initiated work on a simulation code for turbulent pipe flow. It is a pseudo-spectral code with Chebyshev polynomials for the representation in the radial direction. This results in algebraically rather complex equations but enables solution by fast transform methods. This work is still in progress.

Publications: 35

Turbulent boundary layers at high Reynolds numbers and new wind-tunnel design techniques

Researchers: Arne Johansson, Jens Österlund, Björn Lindgren

Sponsors: NUTEK, The Göran Gustafsson Foundation

For turbulent boundary layers typical Reynolds numbers are in most applications very high, whereas most laboratory experiments have been carried out at low to moderate Re. In the present project boundary layer measurements are carried out in the MTL wind tunnel at KTH, on a 7 m long boundary layer plate and with free-stream velocities up to 50 m/s. This gives Reynolds numbers based on momentum loss thickness of up to 20000 or roughly 20 million based on x, which is realistic for practical applications. Hot-wire anemometry is used with X-probes with box sides down to 0.10 mm. However, severe restrictions in the method have been identified that are coupled to interaction of the thermal wakes from the wires (occurring at low Peclet numbers). Also new types of probe geometries are tested where the thermal interaction between two closely spaced hot-wires is used to infer the magnitude and direction of the velocity. A new traversing equipment especially suited for measurements in the near-wall region has been constructed and new measurements using single and double probe arrangements has been constructed.

Two new types of MEMS (micro-electromechanical system) based wall-shear stress sensors have been included in this effort. The first is one constructed at MIT and is essentially a floating balance approximmately 0.1 tex2html_wrap_inline295 0.1 mm tex2html_wrap_inline297 . The experiences with this has shown substantial needs for improvement of the probe design. The second sensor is one constructed at UCLA and is a multi-sensor arrangement with 128 sensors in an array confined to approximately one cm tex2html_wrap_inline297 . The basic principle for this sensor is hot-film anemometry.

Publications: 98

Development of 3D LDV measurement techniques with applications to wall bounded shear flows

Researchers: Rolf Karlsson, Jan Eriksson

Sponsors: NUTEK, Vattenfall Utveckling AB

The aim of the project is to develop a practically useful methodology for making simultaneous 3D LDV measurements with high spatial and temporal resolution, and to apply this technique to obtain detailed 3D turbulence data in the plane turbulent wall jet. In a longer perspective, such data will be used to improve near-wall Reynolds stress turbulence modelling. The first phase of the project has now been successfully completed, and measurements in an enclosed circular jet with a measuring volume as small as tex2html_wrap_inline301 have been made.

The second phase of the project is to supplement an earlier (2D) experimental investigation of the turbulent wall jet with simultaneous 3D measurements of the total velocity vector. In particular, attention will be focussed on the equation for the turbulent kinetic energy and on the limiting behaviour of the Reynolds stresses near the wall. Such measurements are presently going on.

The 3-component LDV measurements of phase 2 have now been concluded, and a thorough analysis of the results is performed. A paper describing the 2-component measurements has been written (ref. 1) and has been accepted for publication in Exp. Fluids. This experiment has also been used as a test case at the ERCOFTAC/IAHR Workshop on Refined Flow Modelling, Paris April 1996 and will also be used in the next workshop in Delft June 1997.

Together with Prof. W.K. George, USA, and a group at Chalmers Univ. of Technology, a similarity theory of the plane wall jet is under development.

Publications: 20,77,89

Hypersonic afterbody flow fields

Researchers: Tor-Arne Grönland, Anders Dahlkild Sponsors: ESA

This work is part of a research project performed external to KTH by the team FFA and DASA. The aim of the study is to make a thorough and basic investigation of the importance of different physical and geometrical effects which influence the efficiency and versatility of a hypersonic afterbody design. The complete propulsion system is an integrated part of the airframe of a hypersonic airbreathing vehicle. The vehicle body will act as expansion surface, yielding an unsymmetric expansion of the engine exhaust gases to the surrounding pressure. In the design of such an afterbody there are a number of critical issues of which one needs a thorough knowledge.

Publications: 78,104,105


Large Eddy Simulation of swirling jets

Researchers: Magnus Olsson, Laszlo Fuchs

Sponsor: TFR

"Dynamic" Large-Eddy-Simulations (D-LES) have the advantage that the model is parameter free. It also offers the possibility of treating transitional flows as the model "shuts" itself "down" in laminar regions. One of the main issues that is addressed here is the way of determining the validity of the basic assumption that the model has reached an "asymptotic" behaviour. Furthermore, one has to be able to distinguish between the truncation errors and the generalized moments (which may contain numerical errors due to the way the double spatial filtering is carried out!). Furthermore, other "asymptotic" SGS models have also been developed and implemented. The technique has been tested/applied to spatially developing free- and impinging jets and to the mixing (of passive scalar) in such jets.

Publications: 112

Numerical Simulation of Flows of Fluids Containing Small Particles

Researchers: Per J. Olsson, Laszlo Fuchs

Sponsor: NUTEK

In multiphase flow, the models used to describe the presence of particles in a fluid usually ignore the force interaction among particles and a fluid flow governed by the Navier-Stokes' equations. In order to gain some insight into the physical phenomena in a "micro" flow environment, we study the interaction among fixed solid spheres and the surrounding fluid. To study the rheology of such systems, a mixture viscosity is computed from the numerical simulations where a shear flow is applied to a field of spherical particles. Due to the presence of attracting and repelling forces that depend on the geometrical configurations, one expects intensive and complex motion of the particles when they are allowed to move freely.

Publications: 88



6.3 Education didactics

FLIP-Flexible Learning in Physics and Mechanics

Researcher: Christer Johannesson, Göran Karlsson, Ian Cohen

Sponsors: (The Swedish) Council for the Renewal of Undergraduate Education and KTH (central support and Mechanics and Physics departments)

FLIP is a three year project in conjunction with Department of Physics at KTH, Department of Physics at Stockholm University, Department of Mechanics at the University of Linköping, and Department of Mathematics at University of Plymouth, UK. The main intention is to (i) incorporate interactive computer programs in the existing courses; (ii) develop a Learning Center in the teaching program at KTH; (iii) introduce the international computer network as a tool for special assignments and in project work; (iv) develop and introduce new forms for student examination. At KTH and Stockholm University 6 FLIP seminars and workshops have been arranged during the year.

At KTH a special room has been furnished and equipped with 5 PC having Internet connectivity. This is the embryo for the Learning Center. SToMP (Software Teching of Modular Physics), CUPS (Consortium of Upper Physics Software), Optics software from State University of Moldova, and Interactive Physics have been installed on these computers.

SToMP and CUPS have also been entered to the KTHCD 96/97 (Projcet Teknologers Datorkraft). Negotiations for a site license for entering Interactive Physics at KTHCD have been carried has gone on most of the year with Knowledge Revolution in California.


Researcher: Göran Karlsson

Sponsors: Internet Regional Program of The Open Society Institute (The Soros Foundation), USA

The result of the pre-study was at an early stage reported to OSI and led to OSI 5-year contracts between OSI and Taide Network in Lithuania considering one VSAT connection in Chisinau and four VSAT connections to Bucharest, Cluj, Iasi and Timosoara (Romania) all placed at Soros' CPC/CCC centers and with bandwidth of 64 kbit/s. As spin-offs (outside OSI financing) one more VSAT connection has been contracted for Chisinau (Innovation Center Apriori) with bandwidth 128 kbit/s (to be upgraded to 256 kbit/s) and about 20 VSAT connections to Romania (including Politehnica University, Bucharest; 1 Mbit/s to be upgraded to 2Mbit/s).

The result of the study has been communicated and documented in several conference proceedings. A comprehensive report (in French) has also been published by Dr. Roza Dumbraveanu at State University of Moldova, Chisinau in Flash Informatique published by EPFL, Lausanne, Switzerland: Internet in Sommaire du numero special du 3 septembre 1996 - Terra informatica (electronic version to be found at

Establishing an information system and distance work network

Researcher: Göran Karlsson

Sponsors: NUTEK

A national information system (FirstClass BBS from SoftArc Inc.) has been set up at KTH and telephone and Internet connections to similar systems in the other Nordic countries, to the central Nordic server in Nyköping and to the Open university in UK has been established. Similar connections are under configuration to Swedish nodes. The goal is to facilitate efficient information flow between all involved parties within the DELTA project NORDIC Information Broker Initiative. The network will also be set up and configured so it will be capable to function as a distance work arena for different grouping within the NORDIC project and thereby reduce the travel time or meetings among project staff as well as for other involved parties. The system also include fax/voice processing of client interfaces. Due to the developing Internet interface of FirstClass new interfaces information systems (Gopher, WWW, WAIS) will be added during the course of the project.

This project is Work Package 5A of the DELTA project (within the 3rd framework programme) NORDIC Information Broker Initiative: The intention of the project is to develop, through a concerted action programme within the Nordic countries, national and regional nodes for DELTA-related information brokerage and partnership support. The project also aims at facilitating information dissemination and experience exchange through seminars, workshops, and information exchange events on on-going DELTA initiatives. Within the project several educational software houses, UETPs (University Enterprise Training Partnership within the COMETT programme) and information broker companies participate.

Follow up studies of the LEONARDO project INTELEC

Researcher: Göran Karlsson

Sponsors: EU LEONARDO programme

This report has been carried out as a part-funded project in the Leonardo Transitional Measures Programme. It has sought to find ways by which the distance learning material created under the Intelec project, a COMETT Cc initiative, might be made available to a wider market. The conclusions of this report are summarised below:

1. The marketing plans from the original Intelec project have been critically reviewed, and found to be inappropriate for today's market. The only viable marketing option is to place the material in the hands of a publisher with an international market base. This view is substantiated by a recent survey on training in the EU. 2. A new partner has joined the Intelec consortium, and has provided valuable marketing information for Scandinavia, the Baltic states, C. & E. Europe. The general conclusion is that in its present form, the material is not suitable for use in these regions. Given that the material is aimed at the vocational level, it is possible that the material would be used if it were translated into the local language. 3. The suitability of electronic publishing for the Intelec material has been considered. At the time of writing, the Intelec learning material is not suitable for multimedia adaptation. 4. Taking into account the above, the proposed exploitation programme for the Intelec material is summarised as:

tex2html_wrap_inline303 Enter into a contract with a publisher
tex2html_wrap_inline303 Establish an EEIG or the equivalent, through which the royalties may be paid to partners
tex2html_wrap_inline303 Review market and use this information to update existing material and create new material.



7 Research activities


7.1 Doctoral theses defended July 1995 - December 1996

Thesis title: Local and nonlocalstability analysis and transition prediction of compressible boundary layer flows

Date: December 15, 1995
Faculty opponent: Dr D Arnal, CERT/ONERA - Aerothermodynamics Department, Toulouse
Evaluation Committee: Prof Lars-Erik Eriksson, Volvo Aero, Prof Håkan Gustavsson, LuTH, Prof Mårten Landahl, MIT.
Main Advisor: Prof. Henrik Alfredsson

The stability characteristics of supersonic boundary layer flows are investigated by means of the local and non-local linear stability theory. The main interest is the effects of yaw angle on the stability characteristics of supersonic boundary layer on a sharp cone. The basic flow is obtained either using the perturbation method or solving the modified boundary layer equations at symmetry planes. The tex2html_wrap_inline30 -method is employed to predict the relative movement of the transition front.

The stability of a flat plate boundary layer at Mach 5 is investigated. The growth rate of both oblique and two-dimensional disturbances are compared to those from the experiments conducted in the Ludwieg-tube facility at DLR at Mach 5. The best agreement is found for the results based on the local stability theory. However, since the orientation of the disturbances in the experiment are not known a detailed comparison is not possible.

The potential for transient growth in compressible boundary layers is studied. Transient amplification is mathematically associated with a non-orthogonal eigenvector basis, and can amplify disturbances although the spectrum of the linearized evolution operator is entirely confined to the stable half-plane. Compressible boundary layer flow shows a large amount of transient growth over a wide range of parameter values. The disturbance size is here measured by a positive definite energy like quantity that has been derived such that press-ure-related transfer terms in its evolution equation mutually cancel. The maximum of the transient growth is found for structures which are independent of the streamwise direction and is found to scale with tex2html_wrap_inline32 . This suggests that the transient growth originates from the same lift-up mechanism found to give large growth in incompressible shear flows. The maximum growth is also found to increase with Mach number.

Ardeshir now has a position as research engineer at FFA.

Thesis title: Studies in classical turbulence theory

Date: May 24, 1996
Faculty opponent: Prof. Claude Cambon, Ecole Centrale de Lyon
Evaluation Committee: Dr Erik Aurell, KTH, Dr Said Zahrai, ABB Corp. Res., Prof. Lars Davidsson, CTH
Advisors: Prof. Arne Johansson and Dr Anthony Burden.

The thesis deals with various problems in classical turbulence theory. The kinematical theory of homogeneous axisymmetric turbulence is given a simple and concise formulation. A representation of two-point correlation tensors of homogeneous axisymmetric turbulence is developed, such that each measurable correlation corresponds to a single scalar function, and moreover such that the equations of continuity take the most simple form. The Poisson equation for the pressure-strain tensor is solved in terms of measurable velocity correlations.

Kolmogorov's third order structure function law is derived from an equation where the pressure terms and mean flow gradient terms are retained. A new inertial range law, relating the two-point pressure-velocity correlation to the single-point pressure-strain tensor, is derived. This law shows that the two-point pressure-velocity correlation, just as the third order structure function, grows linearly with the separation distance in the inertial range. An inertial range law is also derived for the third order velocity-enstrophy structure function of two-dimensional turbulence.

The turbulence closure problem is analysed, starting from the hierarchy of single time Fourier moment equations. The geometric properties of the equation hierarchy are investigated. The number of independent components of the n:th order isotropic correlation tensor of Fourier velocity components is proved to be n+1 for tex2html_wrap_inline38 . It is shown that a closure on the fourth order level would lead to inconsistencies. It is argued that the energy spectrum decreases slower than tex2html_wrap_inline40 in the dissipation range. Here, b is any positive constant.

A comparison between EDQNM and DNS calculations of axisymmetric low Reynolds number turbulence is presented. The agreement between the results is found to be rather good. However, it is argued that this does not permit us to draw any conclusion for the high Reynolds number case.

The prediction capability of pressure-strain models, within the context of RST-closures, is investigated. Severe difficulties are found when the antisymmetric, rotational part of the mean flow gradient tensor, has a stronger influence than the symmetric part.

Erik has in April 1997 started as a research associate at the Department of Mechanics.



7.2 Licentiate theses presented July 1995 - December 1996

Thesis title: Large eddy simulation of spatially developing jets.
Advisor: Prof. Laszlo Fuchs

Magnus presented the thesis at a licentiate seminar in October 1995 and is continuing his graduate studies towards a doctoral degree.

Thesis title: On modelling of dewatering in twin-wire blade forming process.
Advisor: Prof. Fritz Bark

Sima presented the thesis at a licentiate seminar in November 1995 and is continuing her graduate studies towards a doctoral degree.

Thesis title: Local analysis of grazing bifurcations in impact oscillators with several degrees of freedom.
Advisor: Prof. Martin Lesser.

Mats presented the thesis at a licentiate seminar in November 1996 and is continuing his graduate studies towards a doctoral degree.



7.3 Conferences

The first annual meeting of the Nordic PC, which was held at Thoresta Herrgard outside of Stockholm, September 4-6, 1996, was partially supported by the TFR grant. The meeting was organized by the Pilot Center Coordinator Dan Henningson. The meeting provided a very good insight into what is going on in the area of fluid mechanics in the Nordic countries. There were a total of 26 participating senior researchers, four from Denmark, four from Finland, three from Norway and fifteen from Sweden.

The 9th Polish-Swedish Symposium on Mechanics was held in Zakopane 7-12 November 1995 and was combined with the international conference `Nonlinear Dynamics, Chaotic and Complex Systems'. Eight Swedish participants (seven from the mechanics department) gave contributions in the area of non-linear mechanical problems. A total of 150 pqpers were presented at the conference. Some new Swedish - Polish collaboration efforts were also planned during the conference.



7.4 Publications 1995-



Published (and accepted) papers in archival journals and books

  1. Apazidis, N., Lesser, M.B. 1996 On generation and convergence of polygonal-shaped shock waves. J. Fluid Mech. 309, 301-319.
  2. Aronsson D., Johansson, A.V. & Löfdahl, L. 1996 Shear-free turbulence near a wall.J. Fluid Mech. 338 363-385.
  3. Bark, F.H. 1995 Book review: Hydrodynamics of suspensions by M. Ungarish. J. Fluid Mech., 290, 406-408.
  4. Bark, F.H. & Alavyoon, F. 1995 Free convection in an electrochemical system with nonlinear reaction kinetics. J. Fluid Mech. 290, 1-28.
  5. Bech, K.H., Tillmark, N., Alfredsson, P.H. & Andersson, H.I. 1995 An investigation of turbulent plane Couette flow at low Reynolds numbers. J. Fluid Mech. 286, 291-325.
  6. Dahlqvist, P. 1995 Approximate zeta functions for the Sinai billiard and related systems. Nonlinearity 8, 11-28.
  7. Dahlqvist, P. 1995 Periodic orbit asymptotics for intermittent Hamiltonian systems. Physica D 83, 124-142.
  8. Dahlqvist, P. 1995 On the duality between periodic orbit statistics and quantum level statistics. J. Phys. A, 28, 4733.
  9. Dahlqvist, P. 1996 Lyapunov exponents and anomalous diffusion of a Lorentz gas with infinite horizon using approximate zeta function. J. Stat. Phys. 84, 773.
  10. Dahlqvist, P. & Artuso, R. 1996 On the decay of correlations in Sinai billiards with infinite horizon. Phys. Lett. A 219, 212.
  11. Dahlqvist, P. The Lyapunov exponent in the Sinai billiard in the small scatterer limit. To appear in Nonlinearity .
  12. Dahlqvist, P. The role of singularities in chaotic spectroscopy. Invited paper to Chaos Solitons and Fractals. To appear.
  13. Dankowicz, H., 1995 The Two-Body Problem with Radiation Pressure in a Rotating Reference Frame. Journal of Celestial Mechanics and Dynamical Astronomy 61 287-313
  14. Dankowicz, H., 1996 Looking for Chaos. An Extension and Alternative to Melnikov's Method. International Journal of Bifurcation and Chaos, 6, 485-496
  15. Dankowicz, H.,1996 Analytical Expressions for Stable and Unstable Manifolds in Higher Degree of Freedom Systems. International Journal of Bifurcation and Chaos 6 1997-2013.
  16. Dankowicz, H., Holmes, P.,1995 The Existence of Transverse Homoclinic Points in the Sitnikov Problem. Journal of Differential Equations 116 468-483
  17. Dankowicz, H., Holmes, P., Berkooz, G., Elezgaray, J., 1996 Local Models of Spatio-Temporally Complex Fields. Physica D, 90, 387-407.
  18. B.O. Enflo 1996 Saturation of nonlinear spherical and cylindrical sound waves, J. Acoust. Soc. Am. 99, 1960-1964.
  19. Enflo, B. O. 1996 The sound field in the center of a nonlinear bounded beam,J. Tech. Phys.37, 485-487.
  20. Eriksson, J.G. & Karlsson, R.I. 1995 An investigation of the spatial resolution requirements for two-point correlation measurements using LDV. Exp. in Fluids 18, 393-396.
  21. Essén, H. 1995 A study of lattice and magnetic interactions of conduction electrons. Physica Scripta, 52, 388-394.
  22. Hanno Essén & Arne Nordmark 1996 Some results on the electrostatic energy of ionic crystals. Can J. Chem 74 885-891.
  23. H. Essén 1996 Darwin Magnetic Interaction Energy and its Macroscopic Consequences. Physical Review E 53 5228-5239.
  24. H. Essén & M. Svensson 1996 Calculation of Coordinates from Molecular Geometric Parameters and the Concept of a Geometric Calculator. Computers & Chemistry 20 389-395.
  25. H. Essén 1996 A Simple Mechanical Model for the Shape of the Earth European Journal of Physics 17, 131-135.
  26. Gravador, E., Thylwe, K.-E. & Hökback, A. 1995 Stability transitions of exact periodic responses in undamped Helmholtz and Duffing oscillators. J. Sound. Vibr. 182, 209-220.
  27. Hallbäck, M., Henningson, D.S., Johansson, A.V. & Alfredsson, P.H. 1996 Turbulence and transition modelling. Kluwer.
  28. Hanifi, A., Schmid, P.J. & Henningson, D.S 1996 Transient growth in compressible boundary layer flow. Physics of Fluids 8, 826-837.
  29. Hedberg, C.M. 1996 Influence of phase between original frequencies on nonlinear generation of new harmonics. Examples of application from nonlinear acoustics. J. Acoust. Soc. Am. 99 3329-3333.
  30. Henningson, D.S 1996 Comment on ``Transition in shear flows. Nonlinear normality versus non-normal linearity'' [Phys. Fluids 7, 3060 (1995)] Phys. Fluids 8, 2257-2258.
  31. Kapitaniak, T. Thylwe, K.-E., Cohen. I. & Wojewoda, J. 1995 Chaos-Hyperchaos Transition. Chaos, Solitons and Fractals 5, 2003-2011.
  32. Kapitaniak T. & Thylwe K.-E., 1996 Monotonic Stability, Chaos, Solitons and Fractals 7, 1441-1445.
  33. Kapitaniak T. & Thylwe K.-E., 1996 On transverse stability of synchronized chaotic attractors. Chaos, Solitons and Fractals 7, 1569-1581.
  34. Kharkats, Y.I., Sokirko, A.V. & Bark, F.H. 1995 Properties of polarization curves for electrochemical cells described by Butler-Volmer kinetics and arbitrary values of the transfer coefficient. Electrochimica Acta, 40, 247-252.
  35. Komminaho, J, Lundbladh, A & Johansson, A.V. 1996 Very large structures in turbulent plane Couette flow. J. Fluid Mech. 320, 259-285
  36. Lesser, M.B. 1995 The analysis of complex nonlinear mechanical systems: a computer algebra assisted approach. World Scientific.
  37. Lesser,Martin 1995 Thirty years of liquid impact research: a tutorial review. Wear 186 28-34.
  38. Levenstam, M. & Amberg, G. 1995 Hydrodynamical instabilities of thermocapillary flow in a half zone. J. Fluid Mech. 297, 357-372.
  39. Levenstam, M., Amberg, G., Carlberg, T. & Andersson, M. 1995 Experimental and numerical studies of thermocapillary convection in a floating zone like configuration. J. Crystal Growth, 158, 224-230.
  40. Lindborg, E. 1995 Kinematics of homogeneous axisymmetric turbulence. J. Fluid Mech., 302, 179-201.
  41. Lindborg, E. 1996 A note on Kolmogorov's third order structure function law, the local isotropy hypothesis and the pressure-velocity correlation. J. Fluid Mech. 326 343-356.
  42. Matsubara, M. & Alfredsson, P. H. 1996 Experimental study of heat and momentum transfer in rotating channel flow. Phys. Fluids 8, 2964-2973.
  43. Nyberg, C. 1995, The sound field from a point source above a striped impedance boundary. Acta Acustica 3, 315-322.
  44. Nyberg, C. 1996, Nonlinear generation of combination frequencies in closed tubes. J.Tech.Phys. 37, 307-310
  45. Olivas, P., Zahrai, S. and Bark, F.H. 1996 On unsteady electrochemical coating of a cylinder at moderately large Reynolds number. To appear in J. Appl. Electrochem.
  46. Olsson, P.J. & Henningson, D.S. 1995 Optimal disturbance growth in watertable flow. Stud. Appl. Math. 94, 183-210.
  47. Rehbinder, G. & Apazidis, N. 1995 Motion of a torsion pendulum immersed in a linear viscous liquid. J. Sound & Vibration. 184, 745-758.
  48. Sokirko, A.V. & Bark, F.H. 1995 Diffusion - migration transport in a system with Butler - Volmer kinetics, an exact solution. Electrochim. Acta, Acta 40:12, 1983 -1995.
  49. Sundström, L.-G. & Bark F.H. 1995 On morphological instability during electrodeposition with a stagnant binary electrolyte. Electrochim. Acta 40, 599-614.
  50. L.-G. Sundström and S. Kimura 1996 On laminar free convection in inclined rectangular enclosures. J. Fluid Mech. 313, 343-366.
  51. Thor, A. 1995 Terminology for quantities and units in International Standards. ISO Bulletin 26, 7.
  52. Thor, A. 1995 Keeping in line with the International System of Units ISO Bulletin 26, 11.
  53. Thor, A. 1995 Terminology:The spelling of SI units. ISO Bulletin 27, 4.
  54. Thylwe, K.-E. & Bensch, F. 1995 Semiclassical narrow-tube quantizations of time-periodic Hamiltonian oscillators. J. Phys. A: Math. Gen. 27, 7475-7490.
  55. Thylwe, K.-E., Dankowicz, H. 1996 Time-Dependent Normal Form Hamiltonian for Dynamical Equilibria. J. Phys. A: Math. Gen., 29, 3707-3722.
  56. Thylwe, K.-E., Dankowicz, H.,1996 Nonlinear Phase-Integral Approximations of Stationary Waves in Nonhomogeneous Systems. J. Phys. A 30 697-710
  57. Thylwe, K.-E. & Gravador, E., 1995 Non-perturbative stability analysis of periodic responses in driven nonlinear oscillators. J. Sound. Vibr. 182, 191-207.
  58. N. Tillmark 1995 On the spreading Mechanisms of a Turbulent Spot in Plane Couette Flow. Europhys. Lett., 32 481-485.
  59. Tu, J.Y. & Fuchs, L. 1995 Evaluation of three-dimensional overlapping grids and Multigrid methods for calculation of flows. J. Num. Meth. in Eng. 38, 259-282.
  60. Wallgren, F., Amberg, G., Hickner, R.C., Ekelund, U., Jorfeldt, L. & Henriksson, J. 1995 A mathematical model for measuring blood flow in skeletal muscle with the microdialysis ethanol technique. J. Appl. Physiol., 79. pp 648-659.
  61. Wallgren, C.F., Bark, F.H. & Andersson, B.-J. 1996 Electrolysis of a binary electrolyte in two-dimensional channel flow. Electrochim. Acta 41:18, 2909 - 2916.
  62. Wallgren, C.F., Bark, F.H., Eriksson. R., Simonsson, D.S., Persson, J. & Karlsson, R.I. 1996 Mass transport in a weakly stratified cell. To appear in J. Appl. Electrochem.
  63. Wendt, V., Simen, M. & Hanifi, A. 1995 An experimental and theoretical investigation of instabilities in hypersonic flat plate boundary layer flow. Phys. Fluids 7, 877-887.
  64. Yagi, T., Stensson,A. & Hardell, C. 1995 Simulation and visualisation of the dynamic behaviour of an overhead power system with contact breaking. Vehicle system dynamics: international journal of vehicle mechanics and mobility, to appear.
  65. Zahrai, S., Bark, F.H. & Karlsson, R.I. 1995 On anisotropic subgrid modeling in Large Eddy Simulations. European Journal of Mechanics B/Fluids, 14, 459-486.
  66. Zahrai, S. & Bark, F.H. 1995 On the fluid mechanics of twin wire blade forming in paper machines. Nordic Pulp and Paper Research Journal, 4, 245-252.



Published (and accepted) papers in conference proceedings

  1. Alfredsson, P.H. & Matsubara, M. 1996 Streaky structures in transition. In Transitional Boundary Layers in Aeronautics. (ed. R.A.W.M. Henkes and J.L. van Ingen), pp. 374-386. Elsiever Science Publishers.
  2. Alvelius, K., Hallbäck, M. & Johansson, A.V. 1996 Investigation of the self-consistency of the Smagorinsky constant and the value of the Rotta parameter at high Reynolds numbers. In Proc. of the Second ERCOFTAC Workshop on Direct and Large-Eddy Simulation. pp B.3.1-10. Grenoble, Sept. 1996.
  3. Andersson, N.-G., Hemström, B., Karlsson, R.I. & Jacobson, S. 1995 Physical Modeling of a Rapid Boron Dilution Transient. Accepted for publication in Proc. of NURETH - 7, Saratoga Springs, N.Y., USA.
  4. Bakchinov, A.A., Westin, K.J.A., Kozlov, V.V. & Alfredsson, P.H. 1995 On the receptivity of a flat plate boundary layer to localized free stream disturbances. In Laminar-Turbulent Transition, Proc. IUTAM Symp. Laminar-Turbulent Transition, Sendai, Sept. 5-9, 1994 (ed. Kobayashi, R.), 341-348. Springer.
  5. Bark, F.H., Kharkats, Yu.I. & Wedin, R. 1996 Joule heating in electrochemical cells. Proc. Third KSME-JSME Thermal Engineering Conference, Kyongju, Korea. Vol 2, 9 - 17.
  6. Berlin, S., Lundbladh, A., Schmid, P.J. & Henningson, D.S. 1995 Spatial simulations of oblique transition in a boundary layer. Advances in Turbulence V, Proc. 5th European Turbulence Conf., July 5-8, 1994, Siena, Italy (ed. Benzi, R.), 31-35. Kluwer.
  7. Ekstrand, P. & Fuchs, L. 1995 Adaptive solution of transonic flows. Proc. of ICES'95 conference on efficient numerical methods. In print.
  8. Elofsson, P.A. & Alfredsson, P.H. 1995 Experiments on nonlinear interaction between oblique Tollmien-Schlichting waves. In Laminar-Turbulent Transition,Proc. IUTAM Symp. Laminar-Turbulent Transition, Sendai, Sept. 5-9, 1994 (ed. Kobayashi, R.), 465-472. Springer.
  9. Enflo, B. O. 1995 Nonlinear planar, cylindrical and spherical acoustic waves in fluids. Invited article in Current Topics in Acoustic Research, Trivandrum, India 1995, in print.
  10. Enflo, B.O. 1996 The sound field in the center of a nonlinear bounded beam, in Nonlinear Acoustics in Perspective, Proc. 14th International Symposium on Nonlinear Acoustics, Nanjing, China, 17-21.
  11. Eriksson, J.G. & Karlsson, R.I. 1995 Flow structure near the front edge of an ice cover. Proc. Seventh Int. Symp. on Appl. of Laser Techniques to Fluid Mechanics, Lisbon.
  12. Grönland, T.A. & Berens, T.M. 1995 Nozzle/afterbody integration for hypersonic vehicles by means of secondary air injection. AIAA-95-6050.
  13. Hanifi, A. & Dahlkild, A. 1995 Stability characteristics of 3D boundary layer on a yawed cone. In Laminar-Turbulent Transition, Proc. IUTAM Symp. Laminar-Turbulent Transition, Sendai, Sept. 5-9, 1994 (ed. Kobayashi, R.), 381-388. Springer.
  14. Henningson, D.S. 1995 Bypass transition and linear growth mechanisms. Advances in Turbulence V, Proc. 5th European Turbulence Conf., July 5-8, 1994, Siena, Italy (ed. Benzi, R.), 190-204. Kluwer.
  15. Henningson, D.S., Berlin, S. & Lundbladh, A. 1995 Spatial simulations of bypass transition in a boundary layer. In Laminar-Turbulent Transition, Proc. IUTAM Symp. Laminar-Turbulent Transition, Sendai, Sept. 5-9, 1994 (ed. Kobayashi, R.), 263-270. Springer.
  16. Johansson, A.V. 1995 The hierarchy of one-point closures and the modelling of rotational effects. Advances in Turbulence V, Proc. 5th European Turbulence Conf., July 5-8, 1994, Siena, Italy (ed. Benzi, R.), 251-255. Kluwer.
  17. Johansson, A.V. & Hallbäck, M. 1995 The hierarchy of one-point closures: Modelling effects of rotation. In Proc. Euroconference on flows dominated be effects of system rotation, curvature or density-stratification, Paris Nov.1995.
  18. Johansson, A.V. & Wallin S. 1996 A new explicit algebraic Reynolds stress model. In Advances in Turbulence 6, pp 31-34. Proc. the Sixth European Turbulence Conference, Lausanne, July 1996, ed. P. Monkewitz, Kluwer.
  19. T. Kapitaniak & K.-E. Thylwe 1995 Tansverse monotonic stability of chaotic attractors, SPIE Proceedings Vol. 2612: Chaotic Circuits for Communication, 37-47.
  20. Matsubara, M. & Alfredsson, P.H. 1995 Experiments on secondary instability of channel flow with body forces. In Laminar-Turbulent Transition, Proc. IUTAM Symp. Laminar-Turbulent Transition, Sendai, Sept. 5-9, 1994 (ed. Kobayashi, R.), 229-236. Springer.
  21. Arne Nordmark, Existence of periodic solutions in grazing bifurcations of impacting mechanical oscillators, International conference on nonlinear dynamics, chaotic and complex systems (NDCCS '95)
  22. Olsson P.J. & Fuchs, L. 1996 Simulation of the Flow Past Multiple Spheres. Proceedings of the third ECCOMAS Computational Fluid Dynamics Conference, 9-13 September 1996, pp78-84.
  23. Persson, N.H. & Karlsson, R.I., 1996; Turbulent Natural Convection around a Heated Vertical Slender Cylinder. Proceed. Eighth International Symposium on Applications of Laser Techniques to Fluid Mechanics, Lisbon.
  24. Schmid, P.J., Reddy, S.C. and Henningson, D.S. 1996 Transition Thresholds in boundary layer and channel flows. Advances in Turbulence VI (Ed. Gavrilakis, S., Machiels, L. and Monkewitz, P.A.), 381-384, Kluwer.
  25. Simen, M., Hein, S., Bertolotti, F., Wendt, W., Hanifi, A. & Henningson, D. 1995 Nonlocal and local instability analysis of hypersonic flows. In Laminar-Turbulent Transition, Proc. IUTAM Symp. Laminar-Turbulent Transition, Sendai, Sept. 5-9, 1994 (ed. Kobayashi, R.), 147-154. Springer.
  26. Sjögren, T. & Johansson, A.V. 1995 Measurement and modelling of the anisotropic dissipation and slow pressure-strain in homogeneous turbulence. Advances in Turbulence V, Proc. 5th European Turbulence Conf., July 5-8, 1994, Siena, Italy (ed. Benzi, R.), 486-490. Kluwer.
  27. Sjögren, T.I.Å. & Johansson, A.V. 1996 Measurement of pressure-strain through two-point velocity correlations in homogeneous axisymmetric turbulence. In Advances in Turbulence 6, pp 491-494. Proc. the Sixth European Turbulence Conference, Lausanne, July 1996, ed. P. Monkewitz, Kluwer.
  28. Tillmark, N. & Alfredsson, P.H. 1995 Structures in turbulent plane Couette flow obtained from correlation measurements. Advances in Turbulence V, Proc. 5th European Turbulence Conf., July 5-8, 1994, Siena, Italy (ed. Benzi, R.), 502-507. Kluwer.
  29. Tillmark, N. & Alfredsson, P.H. 1996 Experiments on rotating plane Couette flow. In Advances in Turbulence VI (ed. Gavrilakis, S., Machiels, L. and Monkewitz, P.A.), 391-394. Kluwer.
  30. Wallin, S. & Johansson, A.V. 1996 A new explicit algebraic Reynolds stress model including an improved near-wall treatment. In Flow Modeling and Turbulence measurements VI, pp 399-406. Proc. of the 6th international symposium on flow modeling and turbulence measurements. Talahassee, Sept. 1996. Eds C.-J. Chen, C. Shih, J. Lineau and R. Kung. A.A.Balkema, Rotterdam.
  31. Wikström, P., Johansson, A.V. & Hallbäck, M. 1996 Measurements and modeling of temperature fluctuations in a heated cylinder wake. In Flow Modeling and Turbulence measurements VI, pp 143-150. Proc. of the 6th international symposium on flow modeling and turbulence measurements. Talahassee, Sept. 1996. Eds C.-J. Chen, C. Shih, J. Lineau and R. Kung. A.A.Balkema, Rotterdam.
  32. Österlund, J.M. & Johansson, A.V. 1995 Dynamic behaviour of hot-wire probes in turbulent boundary layers. Advances in Turbulence V, Proc. 5th European Turbulence Conf., July 5-8, 1994, Siena, Italy (ed. Benzi, R.), 398-402. Kluwer.


Technical reports and preprints

  1. Bäuerle, L., Levenstam, M. & Amberg, G. 1995 Instability of thermocapillary convection in a cylindrical container, Phys. Fluids, submitted.
  2. Cottereau, S. & Van Mele P. 1995 On shock waves in a parabolic reflector. TRITA-MEK TR 95:8 (Master thesis).
  3. Dellby, J. 1995 A geometric shock dynamics approach to liquid impact. TRITA-MEK TR 1995:1 (Licentiate thesis).
  4. Fukugata, K., 1995; Simulation of particle motion in a turbulent velocity field, part I. SECRC/KB/TR-95/162E (Technical Report, ABB Corporate Research).
  5. Fukugata, K. & Zahrai, S., 1996; Simulation of particle motion in a turbulent velocity field, part II. SECRC/KB/TR-96/107E (Technical Report, ABB Corporate Research).
  6. Grönland T.A., Cambier J.L., 1996 Sensitivity to Physical Modelling for Nozzle/Afterbody Flowfields, FFA TN 1996-13.
  7. Grönland T.A., 1996 Three-dimensional Navier-Stokes Computations on the HYTEX R-A3 Vehicle, FFAP-B-013.
  8. Henningson, D.S. & Alfredsson, P.H. 1995 Research on by-pass transition at the Swedish ERCOFTAC PC. ERCOFTAC bulletin 24, 44-47.
  9. Henningson, D. S. and Lundbladh, A. 1995 Evaluation of Turbulence Models from Direct Numerical Simulations of Turbulent Boundary Layers. Technical Report FFA-TN 1995-09, Aeronautical Research Institute of Sweden, Bromma.
  10. Kharkats, Yu.I., Bark, F.H. & Wedin R. 1996 On the theoretical apects of thermal effects in electrochemical cells. Paper submitted to Electrochim. Acta.
  11. Levenstam, M., Amberg, G., Carlberg, T. & Andersson, M. 1995 Experimental and numerical studies of thermocapillary convection in a floating zone like configuration. J. Crystal Growth, submitted.
  12. A. Nordmark & H. Essén 1996. Hopprepskurvan (The Skipping-rope Curve; in swedish) Elementa (to appear)
  13. Nordstrom, J., Nordin, N. & Henningson, D.S. 1996 The Fringe Region Technique Used in the Direct Numerical Simulation of the Incompressible Navier-Stokes Equations. Submitted
  14. Olsson, M. & Fuchs, L. 1995 Large eddy simulation of a spatially developing circular jet using a dynamic SGS-model. Phys. Fluids., submitted.
  15. Quaireau, C. 1995 Experimental study of oscillatory thermocapillary convection (Master thesis).
  16. Lars Söderholm 1995 Pendeln och Hyperion. Astronomisk Tidskrift 28, 7-11.
  17. Tillmark, N. 1995 On the spreading mechanisms of a turbulent spot in plane Couette flow. Europhys. Lett., submitted.
  18. Wallgren, C.F., Bark, F.H. & Andersson, B.-J. 1995 Electrolysis of a binary electrolyte in two - dimensional channel flow. Electrochim. Acta, submitted.
  19. Wallgren, C.F., Bark, F.H. Eriksson, R., Simonsson, D.S., Persson, J. & Karlsson, R.I. 1995 Mass transport in a weakly stratified cell. J. Appl. Electrochem., submitted.
  20. Westin, K.J.A. & Henkes, R.A.W.M. 1996 Prediction of bypass transition with Differential Reynolds Stress Models. Technical Report LR-813, Faculty of Aerospace Eng., Delft University of Technology.
  21. Zahrai, S, 1995; On modelling of Dewatering in Twin-wire Blade Forming Process. TRITA-MEK Technical Report 1995:11, ISSN 0348-467X, ISRN KTH/MEK/TR-95/11-SE. Licentiate thesis.
  22. Zahrai, S., Bark, F.H. & Norman, B. 1996 On modelling of dewatering in twin-wire blade forming process. Submitted to J. of Pulp and Paper Sci.



7.5 Seminars

Two series of regular seminars have been given during the period July 1995 - December 1996, namely 'Fikaseminarier' - a fluid mechanics seminar series (coordinated by A. Burden) and Theoretical and Applied Mechanics seminar series (coordinated by L. Söderholm). The seminars given in these together with those of invited spekers, given at the department, are listed below.

September 6, 1995 Koji Fukagata, The Faxén Research Centre:
Simulation of particle motion in a turbulent velocity field

September 13 Ulrike Windecker:
Design of a device for calibration of hot-filmsensors at low velocities in air

September 19 Prof. Satish Reddy, Oregon State University:
Stability of streamwise streaks

September 20 Renaud Lavalley, Dept. of Mechanics:
Direct numerical simulation of homogeneous isotropic turbulence focused on passive scalars

27 September: Sergei Simdyankin, Acoustics Dept., University of Nizhny Novgorod and PDC, KTH:
Numerical and experimental simulation of sound propagation and difraction in model acoustic waveguides.

September 27 Jonas Nycander, teknikum, Uppsala:
Experiments on rotating convection

October 3 Dr Petros Iannou, Harvard University:
Stochastic dynamics of non-normal dynamical systems with application to shear turbulence

October 4 Kjell Rosquist, Dept of Physics, University of Stockholm.
A new formulation of the Toda lattice in terms of a geometric/tensorial Lax pair structure.

October 4 Mark Martinez, STFI:
The force on fibres in low consistency refining

October 10 Dr Petros Iannou, Harvard University:
A theory for the control of shear turbulence

October 11 Harry Dankowicz
Regularized celestial mechanics and radiation pressure.

October 11 Johan Westin, Dept. of Mechanics:
Application of turbulence models to transition at high levels of free stream turbulence

16 October: Haim H. Bau, Dept. of Mechanical Engineering and Applied Mechanics University of Pennsylvania
Active control of flow patterns.

October 18 Erik Aurell:
Predictability in shell models of turbulence

October 25 Martin Lesser and Nicholas Apazidis
On converging shock waves.

October 25 Jens Österlund, Dept. of Mechanics:
Measurements in turbulent boundary layers at high Reynolds numbers

October 26 Mustapha Hammache, EPFL:
Cylinder wakes with spanwise non-uniformity

October 27 Bill George, Buffalo, U.S.A:
Some New Ideas on the Similarity of Turbulent Boundary Layers

November 1 Lars Söderholm
Equations of Flow and Relaxation for Moderately Rare Gases.

November 1 Said Zahrai, ABB Corporate Research:
RST-modelling of conducting liquids under the action of strong magnetic fields

November 8 Stellan Berlin, Dept. of Mechanics:
Oblique Transition in a Boundary Layer Experimentally and Numerically

November 9 George K. Batchelor, Cambridge Univ.:
A life of science

November 15 Dan Borglund
On the search for optimal trajectories to the Moon.

November 15 Torbjörn Sjögren, Dept. of Mechanic:
Measurements of two-point triple correlations and slow pressure-strain in homogeneous axisymmetric turbulence

November 21 Magnus Olsson, Dept. of Mechanics:
Large Eddy Simulations of Spatially Developing Jets, Presentation of a thesis for the Licentiate degree. Moderator: Prof. Lars-Erik Erikson, Volvo Aero Corp. & CTH.

22 November: Peter Gudmundson, Hållfasthetslära.
Constitutive equations with micro structure length scales.

November 27 Sergey N. Gurbatov, Nizhny Novgorod University, Russia.
N-dimensional Burgers' equation and its applications in nonlinear acoustics, theory of turbulence, large-scale structure of the universe.

November 27 Anders Lundbladh, Volvo Flygmotor:
The flow in and performance of a jet engine

November 29 Arne Lundberg, Institutionen for ortopedi, Karolinska Institutet, Huddinge sjukhus.
Problems and solutions in analysis of joint biomechanics.

November 29 Ardeshir Hanifi, Dept. of Mechanics:
Transient growth in compressible boundary layer flows

December 6 Erland Källén, Dept. of Meteorology, Stockholm University:
Numerical modelling of the atmosphere on short and climatic time scales.

December 12 Sima Zahrai, Dept. of Mechanics:
On modelling of dewatering in twin-wire blade forming process, Presentation of a thesis for the Licentiate degree. Moderator: Dr. Farid Alavyoon

December 13 Christian Winkler, Dept. of Mechanics:
Simulation of binary solidification

December 14 Prof. D. Arnal, CERT-ONERA, Toulouse:
Numerical and experimental studies related to skin friction drag reduction problems

December 19 Prof Kozlov, Russia:
On the structure of laminar-turbulent transition in an airfoil profile boundary layer

January 24, 1996 Mats Fredriksson.
Local Analysis of Grazing Bifurcations in Many Degrees of Freedom Systems.

January 24, 1996 Martin Berggren, FFA:
Optimal control of the incompressible Navier-Stokes equations

February 7 Arne Nordmark.
Solving Partial Differential Equations in MatLab.

February 7 Daniel Söderberg, Dept. of Mechanics:
Theoretical and experimental investigation of instabilities in plane liquid jets

February 14 Anders Barany, MSL and KVA.
Interaction of Slow Highly Charged Ions with Carbon-60: a Classical Barrier Approach.

February 14 Paul Andersson, Dept. of Mechanics:
Validation of the PSE method

February 21 Johan Westin, Dept. of Mechanics:
Experiments in a laminar boundary layer subjected to free-stream turbulence

February 28 Per Dahlqvist.
Hydrodynamic Formulation of Quantum Mechanics.

February 28 Björn Lindgren, Dept of Mechanics, KTH:
Measurements of guide-vane performeance in diffusing bends for wind tunnels

March 6 Daniel Simonsson, Tillämpad Elektrokemi:
Introduction to chemical and fluid dynamical processes in electrochemical cells

March 13 Casper Hildings, Dept of Mechanics, KTH:
DNS of separation bubbles

March 20 Hans Rickman, Observatory, University of Uppsala.
Resonances and the chaotic routes of meteorites.

March 20 Masaharu Matsubara, Dept of Mechanics, KTH:
Similarity between transition in rotating boundary layer and channel flow

March 27 Martin Zimmermann, Dept. of Quantum Chemistry, Uppsala.
Bifurcation of coherent structures in reaction-diffusion equations.

March 27 Harry Dankowicz, Dept of Mechanics, KTH:
Evolving Control Strategies for Low-Dimensional Models of the Turbulent Boundary Layer

March 29 Dr. Bill Saric, Arizona:
Leading-edge receptivity to sound

April 3 Rebei Bel Fdhila, ABB:
Upward turbulent bubbly flow in a sudden pipe expansion

April 10 Marcello Anile, Department of Mathematics, University of Catania, Italy.

April 10 Martin Skote, Dept of Mechanics, KTH:
Direct numerical simulation of turbulent boundary layer flows in an adverse pressure gradient

April 17 Robert Tönhardt, Dept of Mechanics, KTH:
Crystal growth and dendritic solidification

April 24 Håkan Eliasson, Department of Mathematics, KTH.
The convergence of Lindstedt series and KAM-Theory.

April 24 Kenny Breuer, MIT:
A micro-machined shear-stress sensor

May 8 Stig Lundbäck, Humanteknik AB:
The heart, a `new' type of mechanical pump

May 15 Erik Lindborg, Dept of Mechanics, KTH:
Kolomogorov's third-order structure function law

May 22 Christer Nyberg.
Nonlinear generation of combination frequencies in closed tubes.

May 22 Renaud Lavalley, Dept of Mechanics, KTH:
Stability of buoyant thermocapillary convection

May 29 Bengt Enflo.
Shockwaves in sound beams.

May 29 Per Kjellgren, Dept of Light Construction, KTH:
Finite Element Analysis of Incompressible Flow

5 June: Debabrata Biswas, Bombay.
Quasi-classical Quantization with Arbitrary Trajectories.

June 12 Ruud Henkes, Delft:
Transition of natural-convection flows in differentially heated enclosures

June 19 Dirk Franzmann:
Transition modelling based on an extended single-point closure

August 29 Knut Bech, NTH:
Plane turbulent Couette flow subject to system rotation

August 30 Johan Sundell:
Fluid Mechanical aspects of cooling of rectifier cabinets (a Diploma thesis presentation)

September 4 Gabor Vattay, Solid State Physics Department, Eötvös University, Budapest.
Quantum Chaos and Mesoscopic Systems.

September 5 Magnus Olsson, Dept of Mechanics, KTH:
Amplified frequencies in a circular jet

September 10 Mikael Sima:
Modelling crystallization of sucrose (Mikael is a doctoral student of Dept of Mechanics who works at James Cook Univ. Townsville, Australia)

September 12 Krister Alvelius, Dept of Mechanics, KTH:
Investigation of the self-consistency of the Smagorinsky constant and the value of the Rotta parameter at high Reynolds numbers

September 18 Jesper Adolfsson.
Modelling and simulation of Human and walking Robots Locomotion. Report from a summer school.

September 24 Pedro Olivas, Dept of Mechanics, KTH:
CFD modelling of continuous electroplating

October 1 Lars-Göran Sundström, Dept of Mechanics, KTH:
Diffusion in porous media

October 3 Eric Peirano, Dept. of Energy Conversion, Chalmers:
Modelisation and simulation of turbulent gas-solid flows with applications to circulating fluidized bed boilers (a Faxén seminar)

October 7 Prof. Yasu Kohama, Institute of Fluid Science, Tohoku University, Sendai, Japan:
Effect of micron-sized roughness and sound receptivity on a swept wing boundary layer transition

October 9 Karl-Erik Thylwe.
Time-dependent Normal Form Hamiltonian and a Nonlinear WKB approximation.

October 10 Jan Hemmingson, IFM, Linköping:
Granular materials - their importance to science and industry

October 15 Erik Lindborg, Dept of Mechanics, KTH:
Two-dimensional turbulence

October 17 Christer Fureby:
Large Eddy Simulation of isotropic turbulence, turbulent flow in a channel, and turbulent flow past a square obstacle

October 22 Francois Gurniki, Dept of Mechanics, KTH:
Turbulent free convection in large electrochemical cells with a binary electrolyte

October 23 Harry Dankowicz.
Complex dynamics of the very small components of the solar system.

October 24 Nagata, Birmingham, England:
Nonlinear behaviour of rotating plane Couette flow

October 29 Peter Yakubenko, Department of Hydraulic Engineering:
Global capillary instabilities in jets

October 30 Per Dahlqvist.
Why Liouville operators are essential for the description of chaos.

October 31 Jens Österlund, Dept of Mechanics, KTH:
Time-resolved measurements of wall shear stress in a turbulent boundary layer

November 5 Jacob Yström, NADA:
On the numerical modeling of concentrated suspensions (a Faxén seminar)

November 14 Carl Häggmark, Dept of Mechanics, KTH:
Investigation of transition in a 2D laminar separation bubble

November 19 Renaud Lavalley, Dept of Mechanics, KTH:
An experimental and numerical investigation of thermocapillary flow

November 25 Lars Eriksson, Bofors:
`Förbränningsförlopp i krutmotorer'

November 28 Per Olsson, Dept of Mechanics, KTH:
Interaction between spherical particles in uniform flow

December 5 Per Elofsson, Dept of Mechanics, KTH:
An experimental investigation of oblique transition in a Blasius boundary layer

December 10 Christian Winkler, Dept of Mechanics, KTH:
An experimental and numerical investigation of the TIG welding process

December 12 Petra Wikström, Dept of Mechanics, KTH:
Measurements and modelling of temperature and velocity fluctuations in a heated cylinder wake



7.6 Presentations by staff during the period July 1995 - Dec. 1996

Listed below are presentations by staff members where conference papers (or similar) were not published (coauthors are given within parenthesis)

H. Alfredsson The effect of background rotation on the stability and turbulence of shear flows, invited seminar at KTH Physics department Friday Colloquium, 961108.

H. Alfredsson: Streaky structures in transition Invited paper presented at Colloquium of the Royal Netherlands Academy of Arts and Sciences: Transitional Boundary Layers in Aeronautics. Amsterdam Dec. 1995.

G. Amberg: American Physical society, 48th annual meeting of the div fluid dynamics, Irvine CA, 19-21 Nov 1995

H. Dankowicz: Local Models of Spatio-Temporally Complex Fields The NATO/ASI workshop on `From Finite to Infinite Dimensional Systems', 1995, Cambridge, England.

H. Dankowicz: Escape of Particles Orbiting Asteroids through Arnol'd Diffusion Conference on Ordinary and Partial Differential Equations, 1996, Dundee, Scotland.

P. Elofsson: Oblique wave transition in plane Poiseuille flow, seminar presented at DLR, Göttingen, 951205.

P. Elofsson: Experimental studies of oblique transition, presented at ERCOFTAC Workshop on Bypass Transition, Abisko, 960417-960420.

B.O. Enflo: The sound field in the center of a nonlinear bounded beam, International Conference on Nonlinear Dynamics, Chaotic and complex systems, NDCCS'95, 7-12 November 1995, Zakopane, Poland.

Mats H. Fredriksson (Arne B. Nordmark): Local Analysis of Grazing Bifurcations in Many Degrees of Freedom Systems. In Proceedings of the International Conference on Nonlinear Dynamics, Chaotic and Complex Systems. Zakopane, November, 1995.

R. Hsieh: Technology Learning Using the Web. Fifth Nordic Conference on Computer Aided Learning, 13-16 August 1995, Stockholm.

R. Hsieh: Computer Aided Distance Research in Mechanics. Ninth Polish-Swedish Symposium on Mechanics, 7-12 November 1995, Zakopane.

C. Häggmark (H. Alfredsson): Investigation of transition in a two-dimensional laminar separation bubble, presented at 1996 APS/DFD meeting 24-26 November 1996, Syracuse, New York, USA.

A. Johansson: On a new explicit algebraic Reynolds stress model Invited talk at ONERA/CERT Oct. 1996.

A. Johansson: A new EARSM and the use of automated code generation for testing turbulence models Invited talk at OAI/NASA Lewis, Dec. 1996.

G. Karlsson:
i) Can Local PBL Initiatives Benefit from International Cooperation? International Workshop on Problem Based Learning - PBL - Stanford University 1995-08-07
ii) MoldNet-Introducing Internet Connectivity in the Republc of Moldova. CAEE'95, Bratislava 1995-09-15
iii) European Distance Education with Networked Users' Tools (Ann Roberts, Univ. of Leeds; G. Karlsson, KTH) Tallinn 1996-05-22 (Invited paper)
iv) `Demonstration av användning av World Wide Web i utbildningen', TeliaKonferens-Teleskolan, Kalmar 1995-10-27
v) `Hur gör man undervisningen effektiv? Om nätverkets pedagogiska funktion', Storforum om IT. NUTEK 1996-05-07
vi) `Demonstration av distansutbildning vid lärarkonferens', Tumba, GrafoMedia Utbildning AB 1995-10-27

Lesser,M.B. Oct. 1996 Euromech Conference on Computer Algebra in Mechanics Co-Chairman Paper on Computer Algebra as a language for mechanics.

M. Matsubara (H. Alfredsson): Free stream turbulence induced boundary layer transition, Presented at APS-meeting, Division of fluid dynamics, Irvine Nov. 1995.

Christer Nyberg: Nonlinear generation of combination frequencies in closed tubes, International Conference on Nonlinear Dynamics, Chaotic and Complex Systems, NDCCC's 95, Zakopane, Poland.

T. Sjögren: Automated code generation for two-point boundary value problems Paper presented at EUROMECH 343, Computerized Symbolic Manipulation in Mechanics, Hamburg October 1995.

K.J.A. Westin (P.H. Alfredsson, A.A. Bakchinov, V.V. Kozlov) Experiments on the receptivity and evolution of a localized free stream disturbance. Presented at EUROMECH Colloquium 353 Dynamics of localized disturbances in engineering flows University of Karlsruhe, April 1-3, 1996.

K.J.A Westin (R.A.W.M. Henkes) Application of turbulence models to transition at high levels of free stream turbulence. Presented at Transition modelling for Turbomachinery III ERCOFTAC Transition SIG workshop Aristotle University of Thessaloniki September 21-23, 1995.

Stellan Berlin (Markus Wiegel & Dan S. Henningson) Oblique transition in a boundary layer (experimentally and numerically)

Per A. Elofsson Experimental studies of oblique transition

Ardeshir Hanifi (Peter J. Schmid, Dan S. Henningson) Transient growth in compressible boundary layer flow

Dan S. Henningson Localized disturbances in parallel shear flows

Masaharu Matsubara Experiments on natural transition in a flat plate boundary layer

K.J.A. Westin (P.H. Alfredsson, A.A. Bakchinov, V.V. Kozlov) Experiments on the receptivity and evolution of a localized free stream disturbance


7.7 Visiting scientists

Professors Peter Schmid, Univ. of Washington Satish Reddy, Oregon State Univ. visited the department during Sept. 1995.

Dr Peteros Ioannou, Harvard Univ. visited the department during Sept.-Oct. 1995.

Prof. Yurij Kharkats, Moskva lommer visited the department during six months from Oct. 1995.

Ivan Pavlov, Univ. of Nizhny Novgorod visited the department during the fall semester 1995.

Professor Bill George SUNY Buffalo, NY visited the department for one month during March 1996.

Mitsuyoshi Kawakami, doctoral student from Tohoku University, Sendai, Japan, visits the department for one year (970801-980730) working on experiments on by-pass transition.

Gabor Vattay, Eötvös Univ, Budapest visited the department one month in August -96.

Gurbatov Sergey, Univ. of Nizhny Novgorod visited the department one month during Nov.-Dec. -96.

Hans Fernholtz, TU Berlin, two days in Dec. -96.
Mikael König, Germany, five days in July -96.
Marcello Anile, Italy, three days in April -96.
William Saric, USA four days in March -96.
Masato Nagata, Univ. of Birmingham, England five days in Oct. -96.
Claude Cambon, Ecole Centrale de Lyon,Frankrike three days in May -96.
Prof. Kohama, Tohoku Univ. Sendai, Japan five days in Oct. -96.
Knut Beck, TU Delft, Holland three days in August -96.


7.8 Visits abroad by staff (>2 weeks)

J. Westin spent 12 months at TU Delft, Department of aeronautics 940920-950930.

P. Elofsson spent 3 months (Oct. 95- Dec. 95) at Hermann Föttinger Institut, TU Berlin.

A. Johansson visited ONERA/CERT in Toulouse for two weeks in October 1996.

A. Johansson and T. Sjögren visited OAI/NASA Lewis Research Center in Cleveland for two weeks in Nov.-Dec. 1996.

L. Söderholm spent one month (Nov.-Dec.) 1996 at the University of Catania, Dept. of Mathematics, Italy.





Other activities

Henrik Alfredsson
tex2html_wrap_inline10 vice chairman of Faculty of Engineering Physics
tex2html_wrap_inline10 member of Swedish National Committee for Mechanics (chairman since Jan 1, 1997)
tex2html_wrap_inline10 member of scientific committee Colloquium of the Royal Netherlands Academy of Arts and
Sciences: Transitional Boundary Layers in Aeronautics. Amsterdam 1995
tex2html_wrap_inline10 reviewer for J. Fluid Mech., Phys. Fluids, Eur. J. Mech. B/Fluids
tex2html_wrap_inline10 opponent at dissertation in fluid mechanics at TU Delft, Dec 96
tex2html_wrap_inline10 opponent at dissertation in fluid mechanics at NTH, Trondheim, June 96

Gustav Amberg
tex2html_wrap_inline10 100 % financing from KTH ('rörlig resurs').
tex2html_wrap_inline10 reviewer for J. Fluid Mech., Physica Scripta, Powder Technology, European Journal of
Mechanics /B.
tex2html_wrap_inline10 Secretary of the Swedish National Committee for Machanics (SNM)
tex2html_wrap_inline10 Visits to University of Pennsylvania, University of Arizona, Stanford University. January
Presented seminars at all three places.

Nicholas Apazidis
tex2html_wrap_inline10 Referee for: Int. J. Multiphase Flow, Journal of Biomechanical Engineering, ASME, Canadian
J. chem. Eng.
tex2html_wrap_inline10 Involved together with M. Lesser, L. Thor and I. Cohen in the development of a new
mechanics course based on the Sophia - computer algebra system developed by M. Lesser.
tex2html_wrap_inline10 Advisor for Bo Johansson

Fritz Bark
tex2html_wrap_inline10 acted as director of the Faxén Laboratory, see separate report.
tex2html_wrap_inline10 acted as chairman for the Swedish National Committee for Mechanics. Term ending 1996
- 12 - 31.
tex2html_wrap_inline10 member of the Scientific and Administrative Councils at Centre International des Sciences
Méchaniques in Udine, Italy. Terms ending 1996 - 12 - 31.
tex2html_wrap_inline10 member of the scientific committee for the 3rd International Conference on Transfer
Phenomena in Magnetohydrodynamic and Electroconducting Flows to be held in September
in Aussois, France.
tex2html_wrap_inline10 member of the editorial board of ZAMP.
tex2html_wrap_inline10 member of two boards of reviewers at doctoral dissertations at KTH
tex2html_wrap_inline10 reviewer for a professorship at CTH.
tex2html_wrap_inline10 reviewer for two positions as lecturer, one at KTH and one at CTH.

Anthony Burden
tex2html_wrap_inline10 KTH coordinator of the Erasmus network Resau STAR 2000
tex2html_wrap_inline10 gave part of a short course on the teaching of mechanics in small groups at the Dept. of
Theoretical Physics and Mechanics, Gothenburg

Ian Cohen
tex2html_wrap_inline10 Leader of a cooperation between Dept. Mech. KTH and `Centre for Teaching Mathematics',
University of Plymouth, UK, in a project of making educational problems in mechanics
available on the internet.

Anders Dahlkild
tex2html_wrap_inline10 involved in the continued development of a course in fluid mechanics for graduate students.
tex2html_wrap_inline10 reviewed manuscripts for ZAMP and Physica Acta.
tex2html_wrap_inline10 involved in the FaxénLaboratory, 'Kompetenscentrum Processteknisk Strömningsmekanik vid

Per Dahlqvist
tex2html_wrap_inline10 Three day visit at NORDITA, Copenhagen, October 1996.
tex2html_wrap_inline10 Member of "Censorkorpset for Fysik", Denmark.
tex2html_wrap_inline10 Reviewed manuscripts for J.Phys A. and Phys.Lett.A.

Bengt Enflo
tex2html_wrap_inline10 Swedish organizer of the Ninth Swedish-Polish Symposium on Mechanics, Zakopane 7-12
November 1995
tex2html_wrap_inline10 gave an invited lecture at the Warsaw Technical University 13 november 1995
tex2html_wrap_inline10 'sakkunnig' for a lecturership in applied physics at the National Defence College (Militärhögskolan),
tex2html_wrap_inline10 served on committee at KTH for judging applications to Göran Gustafssons Stiftelse
tex2html_wrap_inline10 was appointed professor (biträdande professor) at KTH 1 December 1996

Hanno Essén
tex2html_wrap_inline10 50 % financing from KTH LUFT resources.
tex2html_wrap_inline10 study rector at the department
tex2html_wrap_inline10 shares the advisorship for Anders Lennartsson with Martin Lesser
tex2html_wrap_inline10 advisor for Gunnar Maxe
tex2html_wrap_inline10 referee for several journal manuscripts
tex2html_wrap_inline10 vice chairman for 'Föreningen Vetenskap och Folkbildning'

Dan Henningson
tex2html_wrap_inline10 coordinator of the Swedish ERCOFTAC Pilot Center
tex2html_wrap_inline10 member of ERCOFTAC Managing Board and Scientific Program Committee
tex2html_wrap_inline10 reviewer for J. of Fluid Mech., Phys. Fluids, Theor. Comp. Fluid Mech., Appl. Sci. Res.
tex2html_wrap_inline10 Member of Board of Associate Referees of the Journal of Engineering Mathematics

Arne Johansson
tex2html_wrap_inline10 head of department
tex2html_wrap_inline10 member of the Advisory Board for the European Journal of Mechanics/B - Fluids
tex2html_wrap_inline10 member of the Scientific Committee of First International Conference on DNS and LES,
to be held in Louisiana August 1997.
tex2html_wrap_inline10 Evaluated a tenure case for a professorship at Northwestern Univ., Illinois.
tex2html_wrap_inline10 Evaluated a tenure case for a professorship at Univ. of Washington, Seattle.
tex2html_wrap_inline10 Served on a search committe for a professorship at Chalmers.
tex2html_wrap_inline10 Served as an external examiner for a doctoral thesis at Ecole Centrale de Nantes.
tex2html_wrap_inline10 Evaluated a `Habilitation' case at Georg-August-Universität Götting
tex2html_wrap_inline10 Research visit at ONERA/CERT Toulouse two weeks in October 1996.
tex2html_wrap_inline10 Research visit at NASA Lewis/OAI two weeks in Nov.-Dec. 1996.
tex2html_wrap_inline10 reviewed manuscripts for J. Fluid Mech., Physics of Fluids, European Journal of Mechanics
tex2html_wrap_inline10 serving on the scientific advisory board for the Turbulent Shear Flows Conference series
tex2html_wrap_inline10 served on the reference group for the vice rector for research at KTH.
tex2html_wrap_inline10 served on the committee for evaluation of the KTH reorganization.
tex2html_wrap_inline10 served on 'kvalitetsrådet' at KTH.

Göran Karlsson
tex2html_wrap_inline10 Coordinator for Work Package 5A Information Network and Collaborative Environment,
Establishing an information system and distance work network within the DELTA project
NORDIC Information Broker Initiative
tex2html_wrap_inline10 Member of Program and Coordiantion Committees for the conferences:
CALISCE'96, Donostia-San Sebastian July 29 - 31, 1996
Mot bättre vetande, Stockholm October 29 - 31, 1996
CAEE'97, Krakow September 11 - 13, 1997, RUFIS'97, Prague September 25 - 27, 1997
tex2html_wrap_inline10 Member of editorial board for European Journal of Engineering Education
tex2html_wrap_inline10 Member of SEFI's (European Society for Engineering Eduction) working groups
for Computer Aided Engineering Education and for Physics
tex2html_wrap_inline10 Evaluator EU programme INTAS-COPERNICUS, March 1996
tex2html_wrap_inline10 Vice chairman 'Riksföreningen för Elektronisk Kunskapsöverföring' (REK)
tex2html_wrap_inline10 Engaged by American Physical Society and UNESCO Physics Action Council Working Group
Telecommunications Networks for Science for Physics Distance Education and Internet
connectivity for the Philippines
tex2html_wrap_inline10 Engaged by UNESCO Physics Action Council Working Group 2 Telecommunications
Networks for Science for Internet connectivity for the Mumbai region, India

Rolf Karlsson
tex2html_wrap_inline10 Member of the Scientific Program Committee and the Industrial Advisory Committee of
tex2html_wrap_inline10 Member of the Organising Committe of the ERCOFTAC/IAHR/COST Workshop on Refined
Flow Modelling, to be held in Delft June 1997.
tex2html_wrap_inline10 Chairman of the board of "Faxén Laboratory".
tex2html_wrap_inline10 Chairman of the Swedish LDA Association.
tex2html_wrap_inline10 Member of the Scientific Committe of the Conference of Laser Anemometry - Advances and
Applications, to be held in Karlsruhe Sept 1997. Reviewer of papers for the conference.
tex2html_wrap_inline10 Member of the Advisory Committee of the 9th Int. Symp. on Applications of Laser
Techniques to Fluid Mechanics, to be held in Lisbon July 1998.

Martin Lesser
tex2html_wrap_inline10 Featured Speaker (Folke Odqvist Lecturer) at Svenska Mechanics Dagar in Lulea, 1997
tex2html_wrap_inline10 associate Editor of J. of Bifurcation and Chaos
tex2html_wrap_inline10 reviewer for J. of Fluid Mech., Proc. Roy. Soc. of London, J. Bifurcation and Chaos,
European J. of Mech.
tex2html_wrap_inline10 served on the Scientific Committee of 3rd Euromech Solid Mechanics Conference
tex2html_wrap_inline10 member of the Swedish National Committee for Mechanics
tex2html_wrap_inline10 \ served on TFR proposal evaluation committee chaired by Prof. H. Gustavsson.
tex2html_wrap_inline10 member of the Faculty of Engineering Physics Appointment Committee.
tex2html_wrap_inline10 Elected Member of the board of CISM, Udine Italy.

Erik Lindborg
tex2html_wrap_inline10 reviewer for J. of Fluid Mech. and Phys. of Fluids

Christer Nyberg
tex2html_wrap_inline10 50 % financing from KTH LUFT resources.

Lars Söderholm
tex2html_wrap_inline10 \ In the autumn of 1996 visiting professor for one month at the Department of Mathematics,
University of Catania, Italy. Invited by Prof. Marcello Anile.
tex2html_wrap_inline10 Planning a David Enskog day in September 1997, where, among other contributions, a David
Enskog lecture, presented this year by Prof. Yoshio Sone, Kyoto, will be inaugurated.



9 The Faxén Laboratory

A short description of the Faxén Laboratory is given below for the period July 1995 - December 1996. The text in section is an extract (with some modifications) of the separate activity report for the Faxén Laboratory written by the Director Fritz Bark. The mechanics department is the `host' department for the Faxén Laboratory (web address:



9.1 Introduction

The Faxén Laboratory, below referred to as FLA, is a NUTEK competence centre with the goal of making research results and methods in experimental, numerical and theoretical fluid mechanics easily available for the participating industrial partners. It is also a goal to broaden the multidisciplinary knowledge base of fluid mechanics in industrial process technology by means of a research program leading to Licentiate and Doctoral degrees. The costs of this centre are shared equally between KTH, NUTEK, and the following parties from industry:

ABB Corporate Research
ABB Industrial Systems
Alfa-Laval Separation AB
Assi-Domän AB
Eka Chemicals AB
Korsnäs AB
Norzink AS
Permascand AB
Stora Corporate Research
Vattenfall Utveckling AB (The Vattenfall Development Co.)

The following financiers are contributing as `non-signatory' partners: Bo Ax:son Johnson Foundation, Bo Rydin Foundation, Institut Polytechnique de Grenoble (via an agreement of cooperation with KTH), NUTEK (via a contract not included in the Three-party Contract), Swedish Pulp & Paper Research Foundation

Staff from the following departments of KTH are involved in the activities of FLA:

Dept. of Chemical Engineering & Technology
Dept. of Materials Processing
Dept. of Mechanics
Dept. of Pulp and Paper Chemistry & Technology

The inter-disciplinary character of the work at FLA is well illustrated by the names of these departments. Thus they represent no less than three of the different Schools at KTH - Chemistry & Chemical Engineering, Mechanical & Materials Engineering, and Engineering Physics.



9.2 Management and organisation of the Centre

Major decisions about the activities of FLA are made by its Board. The present members of this are: Ann Cornell, Lic.Eng., Eka Chemicals AB, Torsten Holm, MSc, AGA AB, Rolf Karlsson, Professor, Vattenfall Utveckling AB (Chairman until Nov. 1996), Ivars Neretnieks, Professor, Dept. of Chemical Engineering, KTH, Björn Widell, Professor, ABB Industrial Systems (Chairman since Nov. 1996), Anders Wigsten, PhD, Stora Corporate Research

The operative leadership at FLA consists of the following persons:
Professor Fritz Bark, Dept. of Mechanics, KTH - Director
PhD Anders Dahlkild, Dept. of Mechanics, KTH - Scientific secretary

Administration of the Centre is handled by:
Ingunn Wester, Dept. of Mechanics, KTH - administrative head.

The research efforts of Faxén Laboratory are aimed at these four main areas:

Materials processing
Paper technology
Separation technology



9.3 Research performed at Faxén Laboratory

Relevant publications are listed in section 7.4. The Faxén Laboratory arranged a number of seminars listed in section 7.5.



Electrochemical engineering

Participating bodies from industry: ABB Corporate Research, EKA Chemicals AB, Norzink AS, Permascand AB, Vattenfall Utveckling AB.

Other party: Institut Polytechnique de Grenoble.

Electrolysis takes place in baths of electrolyte in so called electrolysers, in which a number of electrodes are immersed, either connected in series or in parallel. Due to the reactions at the electrodes the concentration field varies in space, with the result that the electrolytes weight (per unit volume) will be locally either less or more than the average weight in the bath. Consequently the electrolyte is set in motion by the force of gravity. This motion is nearly always turbulent. Furthermore, in e.g. the production of sodium chlorate, hydrogen gas is generated at the cathode and in the zinc electro-winning process, oxygen gas is evolved also at the anode. Due to drag force between the bubbles and the electrolyte, the upward motion of the bubbles of gas causes turbulent circulation of the electrolyte in the reactor.

Many problems which are closely related to the fluid mechanical phenomena mentioned above, are highly relevant for optimisation of the design of electrolysers. For instance, the exchange of mass at the electrodes should be maximized, which requires a rapid supply of undepleted electrolyte. However, high velocities result in short residence times in the electrolysers, which leads to a lot of electrolyte passing through the electrolyser without being fully used. The development of gas bubbles at the electrodes is often exploited to drive the electrolyte through the electrolyser, but at the same time a large volume fraction of bubbles increases the electrical resistance of the electrolyte, which increases the Ohmic loss of energy. Today, the consumption of energy is perhaps the most critical problem in the electro-chemical process industry.

Experiments involving systems of electrodes developing gas - Researcher: Philip Byrne, Advisor: Daniel Simonsson.

Computing turbulent convection in electrochemical cells - Researcher: François Gurniki, Advisor: Said Zahrai.

Measurement of turbulent ranges in free convection - Researcher: Johan Persson, Advisor: Rolf Karlsson.

Joule heating - computing the phase flow in electrochemical cells- Researcher: Ruben Wedin, Advisor: Fritz Bark.

i) Eka Chemicals AB, Norzink AS and Vattenfall Utveckling AB are represented in the guidance group.

ii) Philip Byrnes's experimental setup of electrodes developing gas will be built by Permascand AB, and the first experiments will be carried out at the Eka Chemicals plant in Sundsvall. LDV equipment for measurements will be supplied by Vattenfall Utveckling AB.

iii) Johan Persson, doctoral student at FLA, is 50% employed by Vattenfall Utveckling AB.

iv) Rolf Karlsson, Vattenfall Utveckling AB, has a 20% special professorship at the KTH Dept. of Mechanics.

v) Said Zahari, ABB Corporate Research, is supervising one of the research students active in this programme.

951015 - 951215 and 960513 - 960612 Prof. Kharkas, Yu.I., A.N. Frumkin Institute for Electrochemistry, Russian Academy of Sciences, Moscow. Joule heating in electrochemical cells.



Paper technology

Participating bodies from industry: Assi Domän AB, Korsnäs AB, MoDo AB/R&D, SCA Research AB, Stora Corporate Research AB.

Other parties: NUTEK, Bo Rydin Foundation, Swedish Pulp & Paper Research Foundation.

In a paper-making machine a suspension of cellulose fibres is turned into a wet mat of fibre by squirting out most of the water. In traditional forming, most of the water is squirted out of the suspension on a moving horizontal filtering net, a so called •wire. The suspension is transferred to the wire by the means of a thin but broad jet from a •head box. The water is then sucked out of the suspension through the wire. However, there are a number of drawbacks in this method. Hydrodynamic instabilities in the interface between the suspension and the air above it will limit the speed at which the process can take place. Furthermore, one-sided de-wa-tering makes the structure of the surface of the paper different on its two sides, which is most inconvenient in he case of for instance printing paper.

These disadvantages can be eliminated to a great extent in modern twin-wire machines. In these the jet from the head box is directed into the space between two almost parallel wires, which are kept close together and at high tension. The pair of wires is then passed over one or more rol-lers or blades which makes the separation between the stream lines increase due to the centrifu-gal force. This leads to an increase in the pressure, which drives the water out of the suspen-sion. This method works reasonably well in actual operation, but the understanding of its basic mechanics is far from complete. A better understanding will almost certainly lead to considerable improve-ments in the method. Basically the quality of the final product, measured by homogeneity and the iso-tropy of the fibres, is determined by the flow in the head box and the flow on and between the wires.

Computing the flow of a wire nip - Researcher: Gerald Audenis, Advisor: Anders Dahlkild.

Mathematical models for dewatering during twin wire forming - Researcher: Nicolas Moch, Advisor: Fritz Bark.

Computing the flow of a stratified headbox - Researcher: Mehran Parsheh, Advisor: Anders Dahlkild.

Experimental and theoretical studies of the stability of plane jets - Researcher: Daniel Söderberg, Advisor: Henrik Alfredsson.

Analysis of the orientation of fibres in a headbox - Researcher: Mats Ullmar, Advisor: Bo Norman.

Numerical models for the flow at twin wire forming - Researcher: Sima Zahrai, Advisor: Fritz Bark.

i) STORA has two representatives in the guidance group.

ii) Projects at STORA in both Falun and Skoghall are planned to be carried out with doctoral students taking an active part.

iii) Mats Ullmar, Sima Zahrai and Nicolas Moch are in constant touch with the Swedish Pulp & Paper Research Institute, and the cost of running the FEX machine on their behalf is borne by the industries taking part in the projects.



Separation technology

Participating bodies from industry: Alfa-Laval Separation AB.

The `heart' of a centrifugal separator consists of a stack of tightly packed conical metal plates, where the separation itself takes place. The laminar, multi-phase flow between the plates has been the subject of a considerable amount of research which, among other things, has resulted in several Ph.D. theses. There exists at present a good physical understanding, as well as reliable computational methods, for this part of the flow in a centrifugal separator. In the vicinity of the plates, however, there are a number of components, such as entrance and exit chambers, distri-bution channels et cetera, in which the flow is usually turbulent.

The principal goal of the proposed project is to exploit modern scientific methodology and new re-sults, in particular new results in the modelling of turbulence, in order to achieve a more favou-rable flow in the components outside the above mentioned plates. For instance, energy losses can be considerably reduced by decreasing the pressure drop. Furthermore, the performance of the separator can be improved by changing the shape of the components, so that unnecessarily large fluctuating strain fields in the turbulent flow are reduced. In this way the break-up of for instance drops in a suspension can be reduced, which result in more efficient separation.

Numerical modelling of the turbulence in the inlet of a separator - Researcher; Jonas Gunnarsson, Advisor: Arne Johansson.

i) Jonas Gunnarsson spends part of his time at Alfa-Laval and is planning an experimental study to be carried out there.


9.4 Economics

The turnover during 1995/96 reached 10,8 MSEK. For the 1996/97 fiscal year there remains a balance to be carried forward of about 1,5 MSEK in cash and 0.7 MSEK in the form of in-kind contributions from the industry partners.

The total cash (in kSEK) contributions for 1995/96 (12 months) from the three major parties amount to:


Further contributions are two NUTEK contracts (925), Bo Rydin Foundation (500), Swedish Pulp & P. Res. Foundation (200), Institut Polytech. de Grenoble (122) and Bo Ax:son J. Foundation (130).

Also in-kind contributions totalling roughly 3MSEK (according to budget) from industry add to the total budget.

9.5 Personnel

The following abbreviations are used for KTH departments and companies:
K (Chemical technology), M (Mechanics), MP (Materials processing), PM (Paper & pulp technology, ABB CRC (ABB Corporate Research), VUAB (Vattenfall Utveckling AB).

Electrochemistry: Philip Byrne (K), François Gurniki (M), Johan Persson (M, VUAB), Ruben Wedin (M)

Materials processing: James Centerstam (MP), Koji Fukagata (ABB CRC), Mats Lind (M), Ola Widlund (M),

Paper technology: Gerald Audenis (M), Nicolas Moch (M), Mehran Parsheh (M), Daniel Söderberg (M), Mats Ullmar (PM), Sima Zahrai (M)

Separation technology: Jonas Gunnarsson (M)



9.6 Miscellaneous

Faxén Laboratory is a member of two international organisations, viz:
- European Research Community on Flow Turbulence and Combustion (ERCOFTAC)
- International Association for Hydromagnetic Phenomena and Applications (HYDROMAG)

In the autumn of 1996 the Swedish Pulp & Paper Research Institute, in a joint project with Faxén Laboratory, started a so-called COST Action aimed at the subject of forming in paper machines, etc.

Late in 1996, in a joint project with Institut Polytechnique de Grenoble and a number of other European research institutes and universities, Faxén Laboratory filed a revised application for funds from the EU programme of "Training and Mobility of Researchers". The specific aim is to bring about exchanges of post-doctorships for the purpose of theoretical and experimental studies of transportation in electrochemical systems.

In the spring of 1996 an application for funds towards planning the formation of a national centre for theoretical and experimental studies of multiphase flows was jointly filed to the SSF by Faxén Laboratory, the Centre for Bio-Process Technology (Professor S.-O. Enfors), Parallel Scientific Computing (Professor B. Engqvist) and the Dept. of Thermo- and Fluid Dynamics at CTH in Gothenburg (Dr. A.-E. Almstedt).

A monthly newsletter from FLA has been circulated via Internet and by regular mail.

A two-day introductory course in CFX (CFDS-FLOW3D) was run on 3 and 5 June, 1996, at KTH. The teachers were: John Keeton, AEA-Technology, Sue Thompson, AEA-Technology, Pedro Olivas, KTH and INPG, Grenoble and Ola Widlund, KTH The course had 12 participants.

13 June, 1995: Meeting of interim board of FLA directly after final negotiations with NUTEK.

5-6 October: ``kick-off" meeting for Faxén Lab. at KTH

20 March: Dinner at Kastellholmen for all staff of Faxén Lab.

10-11 April: Workshop in paper technology at Dalarö.

3-5 June: Introductory course in CFX and CFX Swedish User Group Meeting at KTH.

19 June: Workshop in electrochemical technology at KTH.

26 September: Annual meeting of Faxén Lab. at ABB Industrial Systems in Västerås.