Lattice Boltzmann direct numerical simulation of interface turbulence over porous and rough walls

Turbulent Drag Reduction Using Anisotropic Permeable Substrates

“…As mentioned before, the appearance of drag-increasing Kelvin Helmholtz rollers has been reported over permeable walls by several authors [19, 30, 32]. Therefore, in order to bound the range of optimum parameters, which will be investigated later in the DNSs, we aim to predict the formation of these spanwise-coherent rollers using linear stability analysis.…”

“…It was shown in [1] that Squire’s theorem also holds when the boundary conditions are derived from a Darcy model for the substrate. The same cannot be formally deduced when including a Brinkman term, but based on previous evidence that the Kelvin-Helmholtz rollers are predominantly spanwise-coherent [1, 19, 20, 30, 32], we focus on spanwise-homogeneous modes and perform a two-dimensional, viscous analysis.…”

“…Several authors have noted the appearance of spanwise coherent rollers over permeable substrates [19, 30, 31]. Abderrahaman-Elena and García-Mayoral [1] proposed that the formation of these rollers, originating from a Kelvin-Helmholtz-like instability, would be a possible drag-degrading mechanism over anisotropic permeable substrates.…”

Boundary layer flow interaction with a permeable wall

“…The mechanisms involved in the interaction of flows with rough and permeable surfaces, i.e., foams, perforated sheets, beds of packed spheres, etc., have been experimentally and numerically investigated in numerous studies. 12,[14][15][16][17][18][19][20][21][22] Kong and Schetz 17 studied the effect of small-scale roughness and porosity through the development of the turbulent boundary layers over smooth, rough, and porous surfaces. They found that the porosity of the porous surface can generally shift the wall logarithmic region downward by ∆U + ≈ 3-4 compared to the smooth wall, leading to an increase of the skin friction values by about 30%-40%.…”

Direct numerical simulation of turbulent conjugate heat transfer in a porous-walled duct flow

“…Hence, considerable effort has been devoted to understanding the turbulent flow physics over permeable porous walls. One of the most important effects of a porous medium on turbulence is the wall permeability effect, which significantly enhances turbulence by relaxation of the wall-blocking effects; this leads to an increase in momentum exchange across the porous-fluid interface (Zagni & Smith 1976;Kong & Schetz 1982;Manes et al 2009;Suga et al 2010;Manes, Poggi & Ridol 2011;Kuwata & Suga 2016a). The key parameter that quantifies the wall permeability of a porous wall is the permeability tensor, which is defined in the convection theory for porous medium flow proposed by Darcy (1856).…”