Effect of Favorable Pressure Gradient and Permeable Wall on the Flow Regime in the Boundary Layer

We consider air flow in a plane convergent channel, where the acceleration parameter K remains constant over the entire channel length. The lower permeable wall has a constant wall-normal air flux j_w=V_w/U_e, where negative and positive values correspond to gas suction and air injection, respectively. Such flow can be well approximated by the parabolized two-dimensional momentum and continuity equations for a steady incompressible boundary layer. These equations are supplemented with k-ω-γ turbulence model. The model is able to predict laminar-turbulent transition and flow relaminarization using intermittency factor.
The numerical model of the laminar-turbulent boundary layer was successfully tested on ERCOFTAC experimental data for transitional flows. On the basis of carried out simulations we have formed the map of flow regimes depending on the accelerated flow parameter and the gas suction/injection intensity. There are three areas of the map where transition to turbulence is fully prevented, the developed turbulence regime takes place and relaminarization occurs after the laminar-turbulent transition, respectively. A noticeable conclusion is that the gas injection into the accelerated boundary layer can suppress turbulence.