scholarly journals Drag reduction and transient growth of a streak in a spanwise wall-oscillatory turbulent channel flow

2021 ◽  
Vol 33 (6) ◽  
pp. 065122
Author(s):  
A. Yakeno
Keyword(s):  
Drag Reduction ◽  
Channel Flow ◽  
Turbulent Channel Flow ◽  
Transient Growth

scholarly journals Turbulent channel flow over an anisotropic porous wall – drag increase and reduction

2018 ◽  
Vol 842 ◽  
pp. 381-394 ◽  
Author(s):  
Marco E. Rosti ◽  
Luca Brandt ◽  
Alfredo Pinelli
Keyword(s):  
Drag Reduction ◽  
Channel Flow ◽  
High Speed ◽  
Vertical Direction ◽  
Porous Wall ◽  
Turbulent Channel Flow ◽  
Spanwise Direction ◽  
Normal Velocity ◽  
Porous Walls ◽  
The One

The effect of the variations of the permeability tensor on the close-to-the-wall behaviour of a turbulent channel flow bounded by porous walls is explored using a set of direct numerical simulations. It is found that the total drag can be either reduced or increased by more than 20 % by adjusting the permeability directional properties. Drag reduction is achieved for the case of materials with permeability in the vertical direction lower than the one in the wall-parallel planes. This configuration limits the wall-normal velocity at the interface while promoting an increase of the tangential slip velocity leading to an almost ‘one-component’ turbulence where the low- and high-speed streak coherence is strongly enhanced. On the other hand, strong drag increase is found when high wall-normal and low wall-parallel permeabilities are prescribed. In this condition, the enhancement of the wall-normal fluctuations due to the reduced wall-blocking effect triggers the onset of structures which are strongly correlated in the spanwise direction, a phenomenon observed by other authors in flows over isotropic porous layers or over ribletted walls with large protrusion heights. The use of anisotropic porous walls for drag reduction is particularly attractive since equal gains can be achieved at different Reynolds numbers by rescaling the magnitude of the permeability only.

Drag Reduction in a Turbulent Channel Flow with Hydrophobic Wall

2012 ◽  
Vol 24 (3) ◽  
pp. 458-466 ◽  
Author(s):  
Nowrouz Mohammad Nouri ◽  
Setareh Sekhavat ◽  
Alireza Mofidi
Keyword(s):  
Drag Reduction ◽  
Channel Flow ◽  
Turbulent Channel Flow

scholarly journals Drag reduction in turbulent channel flow using bidirectional wavy Lorentz force

2014 ◽  
Vol 57 (11) ◽  
pp. 2133-2140 ◽  
Author(s):  
LePing Huang ◽  
KwingSo Choi ◽  
BaoChun Fan ◽  
YaoHui Chen
Keyword(s):  
Drag Reduction ◽  
Lorentz Force ◽  
Channel Flow ◽  
Turbulent Channel Flow

Drag reduction in turbulent channel flow with periodically arrayed heating and cooling strips

2006 ◽  
Vol 18 (2) ◽  
pp. 025104 ◽  
Author(s):  
Hyun Sik Yoon ◽  
Osama A. El-Samni ◽  
Ho Hwan Chun
Keyword(s):  
Drag Reduction ◽  
Channel Flow ◽  
Turbulent Channel Flow ◽  
Heating And Cooling

Suboptimal control of turbulent channel flow for drag reduction

1998 ◽  
Vol 358 ◽  
pp. 245-258 ◽  
Author(s):  
CHANGHOON LEE ◽  
JOHN KIM ◽  
HAECHEON CHOI
Keyword(s):  
Shear Stress ◽  
Feedback Control ◽  
Drag Reduction ◽  
Channel Flow ◽  
Turbulent Channel Flow ◽  
Suboptimal Control ◽  
Local Distribution ◽  
Friction Drag ◽  
Control Laws ◽  
Simple Feedback

Two simple feedback control laws for drag reduction are derived by applying a suboptimal control theory to a turbulent channel flow. These new feedback control laws require pressure or shear-stress information only at the wall, and when applied to a turbulent channel flow at Reτ=110, they result in 16–22% reduction in the skin-friction drag. More practical control laws requiring only the local distribution of the wall pressure or one component of the wall shear stress are also derived and are shown to work equally well.

Sign in / Sign up

Export Citation Format

Share Document