Mitigation studies of the airfoil-vortex interaction using Large Eddy Simulation

Numerical investigations of the mitigation of airfoil-vortex interactions (AVI) using Large Eddy Simulation (LES) were performed. Novel passages between the upper and lower surfaces of the airfoil mitigated AVIs. A NACA 0012 airfoil at zero angle of attack and the Smagorinsky sub-grid scale model with Van Driest Damping function were used as a benchmark airfoil. The freestream Reynolds number was 300,000 based on the airfoil chord (c = 0.46 m). The Mach number was M = 0.036. The vortex size had strength of 0.9 m 2/s and a viscous core radius of 0.023 m, following the Lamb-Oseen model. Miss-distance was yv = -0.067 m. The LES AVI results (lift and moment coefficients) for no passage were validated against experimental data and verified against URANS (Unsteady Reynolds Averaged Navier-Stokes) simulation (using a Shear Stress Transport turbulence model). Simulations for a vertical passage (placed a 1/4 chord location, with a width of 0.05c), an inclined 45° passage (yv = -0.067 m), and inclined 45° passage (yv = 0 m) were performed with LES. Finally the inclined 45° passage was simulated with LES at M = 0.25, a vortex strength of 6.3 m2/s and yv = 0 m. Each measured the mitigation of the interaction against the NACA 0012 results with incremental lift coefficient (lift spike) as mitigation. Simulation results indicate mitigation (upwards of 5.3% reduction in the incremental lift coefficient) of lift and moment coefficients for the 45° passage when compared against the benchmark airfoil. There was a noticeable penalty in drag throughout the interaction for the 45° passage. If the Courant number is lower than unity for URANS of AVI, lift/moment predictions with the same computational time as LES are reasonable. LES was determined to be a valid method for BVI investigations.