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  4. Revisiting the drag reduction problem using adjoint-based distributed forcing of laminar and turbulent flows over a circular cylinder
 
research article

Revisiting the drag reduction problem using adjoint-based distributed forcing of laminar and turbulent flows over a circular cylinder

Meliga, P.  
•
Boujo, E.  
•
Meldi, M.
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November 1, 2018
European Journal of Mechanics B-Fluids

This study assesses the ability of a sensitivity-based, span-wise homogeneous control velocity distributed at the surface of a circular cylinder to cut down the cost of reducing drag by more classical techniques, e.g., base bleed and lateral suction. At Reynolds number Re 100, achieving the linear optimal reduction requires a time-dependent control velocity, set at each time instant against the sensitivity of the instantaneous drag. This approach however fails against even small control amplitudes because the system does not have time to adjust to the rapid change in the value of the wall velocity, and drag essentially increases. An efficient (albeit linearly suboptimal) reduction is however achieved using a steady control velocity set against the time averaged sensitivity. By doing so, drag decreases monotonically with the control momentum coefficient, and the sensitivity-based design exhibits a significant advantage over base bleed and lateral suction, that both reduce drag to a far lesser extent. Similar results are reported using various levels of modeling to compute approximations to the exact, time averaged sensitivity. The mean flow approach, that requires knowledge of the sole time averaged cylinder flow, yields especially promising results given the marginal computational effort. This approach is thus extended to the turbulent case at Re =3900, where it achieves similar efficiency in the frame of both 2-D and 3-D RANS modeling. The study concludes with a discussion about the feasibility to extend the scope to span-wise periodic forcing velocities, following the line of thought of Kim and Choi (2005). (C) 2018 Elsevier Masson SAS. All rights reserved.

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Type
research article
DOI
10.1016/j.euromechflu.2018.03.009
Web of Science ID

WOS:000447570200010

Author(s)
Meliga, P.  
Boujo, E.  
Meldi, M.
Gallaire, F.  
Date Issued

2018-11-01

Publisher

ELSEVIER SCIENCE BV

Published in
European Journal of Mechanics B-Fluids
Volume

72

Start page

123

End page

134

Subjects

Mechanics

•

Physics, Fluids & Plasmas

•

Physics

•

flow control

•

drag reduction

•

numerical gradients

•

adjoint method

•

base bleed

•

lateral suction

•

shear-layer instability

•

sensitivity-analysis

•

reynolds-numbers

•

bluff-body

•

wake

•

simulation

•

actuators

•

stability

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
LFMI  
Available on Infoscience
December 13, 2018
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/152465
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