

	Mechanics På svenska

Project

Active Control of Boundary-Layer Transition

Research Area:

Fluid mechanics

Project Members:

Åkervik, E.Å.

Berggren, M

Chevalier, M.C.

Henningson, D.S.H.

Hoepffner, J.P.J.

Högberg, M.

Sponsor:

FOI, NGSSC, VR

Project Description

Study and design of active control strategies for transition in boundary layer flows is done within this project. The control strategies are designed using the optimal-control approach to control of the Navier-Stokes equations and use the adjoint-equation technique for associated gradient computations. Linear optimal control techniques based on the Riccati equation are also explored, where spatially localized convolution kernals have been obtained for both control and estimation. The strategies are applied to control or delay of bypass transition as well as other flow instabilities. The performance of these control laws is quantified in direct numerical simulations by computing transition thresholds. We have shown that the threshold values can be increased by about 500% for random perturbations. By using a physically motivated modification of the objective function we have shown that the linear controllers are also able to relaminarize a low Reynolds number turbulent flow. A new direction of this research is to calculate and evaluate these controllers and estimators for more complicated boundary layer flows such as Falkner-Skan and Falkner-Skan-Cooke flows.

Publications related to the project

Year	Title
2005	State estimation of wall bounded flow systems. Part 1. Laminar flows J. Fluid Mech. 534 263--294 (Published)
2003	Linear feedback control and estimation of transition in plane channel flow J. Fluid Mech. 481 149-175 (Accepted)
2003	Relaminarization of Re_tau=100 turbulence using gain scheduling and linear state-feedback control Phys. Fluids 15 3572-3575 (Submitted)
2003	Linear compensator control of a pointsource induced perturbation in a Falkner-Skan-Cooke boundary layer Phys. Fluids 15 2449-2452 (Accepted)
2002	Linear optimal control applied to instabilities in spatial boundary layers. J. Fluid Mech. 470 151-179 (Published)
2001	Optimal control of transition initiated by oblique waves in channel flow. Turbulence and Shear Flow Phenomena - 2 I 157-161 (Published)
2001	Optimal control of wall bounded flows FOI-R-0182-SE (Published)
2000	Optimal Control of Bypass Transition Advances in Turbulence VIII. (2000) Proc. 8th European Turbulence Conference, Barcelona, Spain 205-208 (Published)
2000	Spatially localized convolution kernels for feedback control of transitional flows 39th IEEE Conference on Decision and Control 4 3278-3283 (Published)
2000	Numerical Approaches to Optimal Control of a Model Equation for Shear Flow Instabilities Flow, Turbulence and Combustion. Kluwer Academic Publishers. 65 (3/4):299-320 (Published)
1999	Numerical investigation of different discretization approaches for Optimal Control FFA TN 1999-74 (Published)
1998	Secondary instability of cross-flow vortices in Falkner-Skan-Coke boundary layers. J. Fluid Mech. 368 339-357 (Published)

Internal Reports related to the project

Year	Title	Document Type
2001	Optimal Control of Boundary Layer Transition	Doctoral thesis