Three Dimensional Microscopic Flow Simulation Across the Interface of a Porous Wall and Clear Fluid by the Lattice Boltzmann Method

The effects of the porous medium on the flow in the interface region between a highly porous wall and clear fluid are discussed. Three dimensional laminar flows in the interface regions of foamed porous walls are microscopically simulated by the lattice Boltzmann method. The chosen porous structure is the body-centered-cubic or the unit cube structure whose porosity ranges 0.82-0.98. The velocity distribution in the interface regions show that the flow penetration into porous layer is very little and it decays until one pore-diameter depth from the interface. To describe the slip velocity distribution independently of the porous structure, the permeability Reynolds number and the friction velocity are confirmed to be representative scale parameters. The stress jump conditions across the interface are also examined with the simulation results. Although the obtained averaged wall friction of the porous interface is slightly lower than that of the solid smooth impermeable surface, the reduction is not significant due to the Reynolds stress arisen from the statistical averaging of the interfacial flow motions.