Control of wall-mounted bluff body wake by a porous substrate*

Unsteady separation and vortex shedding in the wake of bluff bodies result in many adverse effects such as drag increase, vibration, and noise. Flow separation along the wall in the wake of wall-mounted bluff bodies are common in engineering devices and aero/hydro vehicles. Porous substrates have been explored as means of passive control in wall bounded flows since the wall permeability enhances momentum exchange and affects the flow structure over the porous wall, and that potentially affect the formation of a separation bubble as well. A previous experimental study has shown that the recirculation bubble behind a 3D obstacle in the channel vanishes when placed over a porous substrate with high permeability. In the present study, the control of the wall-mounted bluff body wake by using a porous substrate is investigated via flow simulations. The flow over and through the porous medium is simulated by solving the volume averaged Navier-Stokes equations employing the sharp-interface immersed boundary method and the Darcy-Forchheimer model. The effects of the substrate porosity and its size and depth on the strength and stability of the separation are investigated for the flow over a rib in the channel as well as the flow over a wall-mounted dome.