Numerical investigation of dynamic stall suppression of rotor airfoil via improved co-flow jet

Abstract

The decrease in aerodynamic performance caused by the shock-induced dynamic stall of an advancing blade and the dynamic stall of a retreating blade at low speed and high angles of attack limits the flight speed of a helicopter. However, little research has been carried on the flow control methods employed to suppress both the dynamic stall induced by a shock wave and the dynamic stall occurring at high angles of attack. The dynamic stall suppression of a rotor airfoil by Co-Flow Jet (CFJ) is numerically investigated in this work. The flowfield of the airfoil is simulated by solving Reynolds Averaged Navier-Stokes equations based on the sliding mesh technique. Firstly, to improve the effect of a traditional CFJ on suppressing rotor airfoil shock-induced dynamic stall, an improved CFJ—a CFJ-sloping slot is proposed. Research shows that the CFJ-sloping slot suppresses the shock-induced dynamic stall more effectively than a traditional CFJ. Moreover, the improved CFJ can also suppress the dynamic stall of rotor airfoil at low speed and high angles of attack. The improved CFJ proposed in this paper is an effective flow control method that simultaneously suppresses the dynamic stall of the advancing and retreating blades. The mechanism of the improved CFJ in suppressing the dynamic stall of the rotor airfoil is studied, and a comparison is made between the improved CFJ and the traditional CFJ in terms of dynamic stall suppression at high and low speed. Finally, the effect of improved CFJ parameters (the jet momentum coefficient, the position of the injection/suction slot, and the size of the injection/suction slot) on shock-induced dynamic stall suppression is analyzed.