Research progress on rotor reverse flow and dynamic stall flow control methods

When a helicopter flies forward at high speed with heavy load, the blade pitch changes greatly and dynamic stall is prone to occur. The lower rotational speed of the inner section of the trailing blade leads to the formation of a reverse flow zone under the superposition of the incoming flow, resulting in a reduction in the aerodynamic efficiency of the blade. The problems of blade fatigue failure and lift reduction hinder the further improvement of helicopter performance. Flow control methods have great potential in improving the aerodynamic characte-ristics of airfoils, and are effective ways to improve the rotor aerodynamic efficiency and ensure helicopter safety and stability. In this paper, the formation mechanism and unsteady flow characteristics of the reverse flow zone and dynamic stall are firstly described, and the research results of two special aerodynamic phenomena are summarized. On this basis, a comparative analysis of flow control methods such as variable airfoil configuration, surface mechanical devices, air-blowing control, plasma actuator, synthetic jet actuator, and trailing edge flap on the mechanism of rotor dynamic stall and reverse flow control is conducted, and the effects of control parameters and flow field parameters on control effectiveness are summarized. Finally, the remain-ing problems and solutions in the application of various flow control methods are prospected.