Heat transfer enhancement behind a backward facing step using localized suction and blowing

In this numerical study, the effect of suction and blowing with constant mass fluxes on heat transfer enhancement and flow separation behind a backward facing step in a sufficiently long channel is investigated. The simulations have been carried out by a laminar, incompressible, unsteady open-source flow solver (OpenFoam). Using the constant Reynolds number for the base-flow, a systematic investigation of ejections and suctions is performed. The jet-mass flow rate is constant and the flow control is carried out either by suction and blowing from three slots located on the upper, lower wall of the channel and on the vertical step wall. The representative flow fields and the reattachment lengths are reported in an effort to optimize the operation parameters. The velocity and temperature profiles extracted downstream of the slots are then obtained to show that the recirculation zone behind the backward facing step has reduced significantly and the heat transfer is enhanced through better mixing. Based on the friction coefficient and the Nusselt number variation along the bottom wall of the channel, the optimum operating conditions are defined.