Numerical Study of Extreme Adverse Pressure Gradients Enabled by Co-Flow Wall Jet

Abstract

This paper conducts a 2D numerical study of flows with extreme adverse pressure gradients (EAPG) enabled by Co-Flow Jet (CFJ) active flow control (AFC). An EAPG is defined to be an adverse pressure gradient of at least one order of magnitude greater than that which could be sustained by the non-controlled flow of a baseline case. The flow field is solved using the Unsteady Reynolds Averaged Navier-Stokes (URANS) equations with the one-equation Spalart-Allmaras turbulence model. A CFJ cylinder and CFJ airfoil with EAPG and attached flow are studied, showing lift coefficients up to 19.68 and 15.96 respectively. The CFJ airfoil maintains attached flow in a maximum streamwise adverse pressure gradient 1091 times greater than the baseline airfoil, and a maximum radial adverse pressure gradient 121 times greater than the baseline airfoil. Similarly, the CFJ cylinder shows attached flow with a streamwise pressure gradient ratio up to 17 and radial pressure gradient ratio up to 132. Such an extraordinary adverse pressure gradient ratios motivate this effort to investigate how the implementation of the CFJ can achieve this effect. Due to its ability to maintain attached flow in the presence of an EAPG, the CFJ offers a highly effective method of active flow control with the potential to be far more effective than other active flow control devices.