| Abstract: | The effects of two parallel porous walls are investigated, consisting of the Darcy number and the porosity of a porous medium, on the behavior of turbulent shear flows as well as skin-friction drag. The turbulent channel flow with a porous surface is directly simulated by the lattice Boltzmann method(LBM). The Darcy-BrinkmanForcheimer(DBF) acting force term is added in the lattice Boltzmann equation to simulate the turbulent flow bounded by porous walls. It is found that there are two opposite trends(enhancement or reduction) for the porous medium to modify the intensities of the velocity fluctuations and the Reynolds stresses in the near wall region. The parametric study shows that flow modification depends on the Darcy number and the porosity of the porous medium. The results show that, with respect to the conventional impermeable wall, the degree of turbulence modification does not depend on any simple set of parameters obviously. Moreover, the drag in porous wall-bounded turbulent flow decreases if the Darcy number is smaller than the order of O(10-4) and the porosity of porous walls is up to 0.4. |
