Turbulent drag reduction by spanwise oscillations of a channel wall with porous layer

•Turbulent open channel flows with an oscillating wall covered with porous medium layer are investigated by DNS based on LBM.•An analytical solution to Stokes second problem with two different kinds of fluid is derived.•Dependencies of porous medium parameters on drag reduction are shown and a combi...

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Bibliographic Details
Published in:Computers & fluids 2019-02, Vol.180, p.1-10
Main Authors: Li, Qing-Xiang, Pan, Ming, Zhou, Quan, Dong, Yu-Hong
Format: Article
Language:English
Subjects:
Channel flow
Computational fluid dynamics
Computer simulation
Drag reduction
Exact solutions
Fluid flow
Incompressible flow
Mathematical models
Numerical analysis
Porous media
Porous medium
Porous walls
Projects
Spanwise oscillations
Turbulence
Viscosity
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Summary:•Turbulent open channel flows with an oscillating wall covered with porous medium layer are investigated by DNS based on LBM.•An analytical solution to Stokes second problem with two different kinds of fluid is derived.•Dependencies of porous medium parameters on drag reduction are shown and a combined parameter is proposed to describe the correlation.•A strategy to achieve drag reduction in wall-bounded flows is examined. Direct numerical simulations (DNS) are carried out for the incompressible viscous turbulent flows over a spanwise-oscillating porous wall to investigate the effects of the oscillating porous wall on turbulence modifications as well as on turbulent drag reduction. The lattice Boltzmann method (LBM) based on D3Q19 model is applied to perform the numerical computation. Different Darcy numbers and porosities of porous medium are considered to pursue a significant drag reduction. An analytical solution to the Stokes second problem with two different kinds of fluid is derived, which predicts that the presence of porous layer will speed up the oscillation of the fluid when the porous medium is embedded in the Stokes layer. The current strategy suggests that comparing with the effects of the oscillating smooth wall, the joint effects of the porous wall and its spanwise oscillation may attain a larger drag reduction.
ISSN:0045-7930
1879-0747
DOI:10.1016/j.compfluid.2018.12.007