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Article information
Inertia-induced adiabatic structures in time-periodic laminar flows
| Authors: |
Pouransari, Z.,
Speetjens, M.,
Clercx, H.,
|
| Type: |
Conference |
| Pubstate: |
Published |
| Journal: |
7th Eur. Fluid Mech. Conf. EFMC7, Manchester, 14-18 Sept. 2008. |
| Volume: |
1
274 |
| Year: |
2008 |
Abstract
Mixing quality in unsteady incompressible laminar flows can be greatly
enhanced
by three-dimensional (3D) chaotic advection. A significant issue for mixing
applications is the response of invariant surfaces, which the
non-inertial limit (Re=0)
of such flows may admit, to fluid inertia (Re>0). We have studied
topological
properties of a viscous incompressible time-periodic flow in a square
cylindrical
domain. In particular we have focused on the response of the one-action
state to the
inertial perturbations for the general two-step volume preserving maps.
Previous
investigations indicate formation of one coherent structure consisting
of two
incomplete adiabatic surfaces and two tubes with transversal motion in
between, i.e.
resonance-induced merger (RIM) for a specific forcing protocol (one step
forward in
x-direction followed by one step forward in y-direction)1. Here the
adiabatic surfaces
are remnants of perturbed invariant surfaces and tubes are centred upon
elliptic
segments of periodic lines. In this study we have validated and examined the
formation of such coherent structures by RIM for any arbitrary two-step
volume
preserving map. Fundamental topological characteristics of the general
two-step
forcing protocol (as the building block for future protocols) have been
examined
numerically (Fig1-a) and the so called ‘RIM’ phenomena has been detected
in the
neighborhood of parabolic borders (Fig1-b,c). Key aspects of numerical
simulation
results are validated by means of an experimental visualization method.
Furthermore the above analytical and numerical studies have been
extended to the
three-step closed loop map, i.e. bottom wall is translated while
following a triangle.
This enables infinite repetition in a laboratory set-up using finite
walls and thus
facilitates detailed experimental analysis of RIM.
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