Wake structure for flow past and through a porous square cylinder

Numerical simulations have been performed for the flow past and through a porous square cylinder over a wide range of Reynolds numbers (1 ⩽ Re ⩽ 50) and Darcy numbers (10−6 ⩽ Da ⩽ 10−1). It is found that the recirculating wake existing downstream of the cylinder is completely detached from the body under a certain range of parameters. The size and the location of the wake mainly depend on Re and Da. Specially, the wake may initially increase but then decrease in size with an increase in Re, and eventually disappear when the Reynolds number is sufficiently large. The variation of the critical Reynolds number for the onset of recirculating wake as a function of Darcy number is summarized. The results also show that in the range of Da investigated, different from that of the solid cylinder, the recirculating wake is initially developed downstream of the porous cylinder, but not on the surface of it.