Numerical analysis of vortex shedding behind a porous square cylinder

Vortex shedding behind a porous square cylinder is studied by a semi-implicit projection finite element method in this paper. Flow fields over the porous square cylinder with various porosity and Darcy number were calculated to investigate the effects of porous media on Strouhal number, lift and drag coefficients at Re = 100, 200 and 250. The global quantities of the shedding flow appear evident variation for Da varied from 10(-5) to 10(-4). In particular, Strouhal number displays an obvious jump for Da = 10(-4) at Re = 250, due to the variation inflow structure near the cylinder. Larger Darcy number postpones the occurrence of flow fluctuation, and the oscillation flow presents stronger amplitude. However, the flow field and the characteristic values of vortex shedding for Da less than or equal to 10(-6) are almost not changed For different porosity, time histories of CD and CL look similar. In conclusion, Darcy number demonstrates more influence on the flow field than porosity does.