Passive control of shock wave/turbulent boundary layer interaction using low permeability wall ventilation over a supercritical RAE-2822 airfoil

Abstract

The effect of a passive control concept made of a porous surface with a cavity underneath the shock wave/boundary layer interaction on a supercritical RAE-2822 airfoil in a transonic flow regime, is investigated to achieve a better efficiency using a variable porous length with a low permeability factor. A numerical approach is carried out using the commercial ANSYS Fluent code to solve the Reynolds-averaged Navier–Stokes equations of a two-dimensional, fully turbulent, compressible, and steady flow around the airfoil at M_∞ = 0.82, Re_∞ = 2·10⁷, and a 6° angle of attack, with the Spalart–Allmaras turbulence model. Both cases of a clean and a porous configuration, have been studies. The results showed the effect of the control technique by producing a downstream movement of the shock with a larger flow supersonic region and a reduced flow separation zone and thus a weaker SBLI, compared to the clean. Consequently, a lift increase and a drag reduction are obtained, leading to an improvement in the aerodynamic efficiency. Seeking for a higher control efficiency, variable porous surface lengths and low permeability factors, have been tested. The best aerodynamic efficiency was obtained with a full-chord porosity and a low permeability factor of 10⁻⁶, with an appreciable gain in lift of 47 % and a substantial net drag reduction of 65 %.