Active flow control behind a backward facing step using a zero-net-mass-flux system

In this numerical study, the effect of combined suction and blowing with constant mass flux on heat transfer enhancement and flow separation control behind a backward facing step (BFS) in a sufficiently long channel is investigated. The simulations have been carried out by a laminar, incompressible, unsteady open-source flow solver (OpenFoam). Using three different Reynolds numbers for the base-flow (Re = 200, 400 and 600), a parametric investigation of ejections and suctions is performed where the jet configurations are modeled as to produce a zero net mass flux in the channel. The three equally-sized slots for flow control are located on the upper, lower walls of the channel and on the vertical step wall. The magnitudes of jet velocities for suction and blowing are determined with respect to the mean base flow velocity for four different values and jet off-condition. The representative variation of the mean friction coefficient and Nusselt number along the bottom wall downstream the step are reported in an effort to determine the most effective operation condition.