Improved delayed detached eddy simulation of super-lift flow of co-flow jet airfoil

This paper present the improved delayed detached eddy simulation (IDDES) of Co-Flow Jet (CFJ) flow control airfoil, with super lift coefficient that exceeds theoretical lift coefficient limit[1]. The spatially filtered Navier-Stokes equations are solved using a fifth-order WENO reconstruction scheme for the inviscid fluxes and a fourth order central differencing scheme for the viscous fluxes. The IDDES is developed based on the Spalart-Allmaras (S-A) turbulence model and it incorporates the wall modeled large eddy simulation (WMLES) capacity. The simulated wing span is 0.1 chord with periodic boundary condition applied in the spanwise direction. The IDDES simulation of the CFJ wing is carried out at the AoA of 62^◦ with three different jet momentum coefficients C_µ of 0.25, 0.35 and 0.5. The super-lift coefficient of 9.1 is achieved at AoA = 62^◦ and C_µ = 0.5. The baseline NACA6421 wing is also simulated at AoA = 18^◦ and the results show excellent agreement with the experiment. The comparison of the flow field of CFJ-NACA6421 and baseline NACA6421 airfoil shows that the CFJ can remove the flow separation at a high angle of attack. The high momentum jet provides adequate jet momentum to active the boundary layer and maintains the flow attached.The qualitative counter-rotating vortex structures at very high AoA and severe adverse pressure gradient is similar to those observed in 2D RANS simulation.