Self-Noise Effects on Aerodynamics of Cambered Airfoils at Low Reynolds Number

Aerodynamics of cambered airfoils are investigated numerically, using a NACA four-digit series of 6% thickness at low Reynolds number Re=10,000 and moderate Mach number M=0.2, by focusing on the relation of aeroacoustic effects and hydrodynamic flow unsteadiness. Two-dimensional numerical simulations show that the onset of an acoustic feedback loop leads to an abrupt increase in lift force. Associated with the feedback process, the evolution of two-dimensional vortices in the suction-side boundary layer shifts a separation bubble toward the leading edge, which causes a relatively steep pressure recovery near the trailing edge. Through a parametric study on airfoil shape, the aerodynamically favorable feature of aft camber is further enhanced with the presence of an acoustic feedback loop. In addition, the aft camber airfoil successfully forms a laminar separation bubble in three-dimensional calculations at the present Reynolds number, developing transitional behavior on the suction side, supposedly prompted by the airfoil tones. Although the boundary layer shows three-dimensional complexity, still the formation of an acoustic feedback loop is strongly suggested, via the comparison of spanwise correlations.