Dynamic stall formation and control for plunging airfoil: An optimization study of plasma actuator by genetic algorithm approach

This research examines the effects of plunging motion on the formation of the dynamic stall vortex (DSV) over an airfoil and its mitigation using an optimized plasma actuator configuration. A closed-loop genetic algorithm (GA) optimization framework was employed to systematically determine the optimal location (x/c = 0.0–1.0) and duty-cycle frequency (f = 10–1000 Hz) of the plasma actuator for plunging airfoil with amplitudes of A°/c = 0.25–1.00 at Reynolds number of Re=6.6×104. Numerical validation against particle image velocimetry confirms the accuracy of the plasma model in capturing induced-flow physics, revealing three distinct flow patterns at frequencies of 10, 100, and 1000 Hz. When the induced flow couples with the incoming velocity, the DSV is transformed, resulting in an attached shear layer. The GA identifies two amplitude-dependent flow control patterns: (1) At A°/c = 0.25 and 0.50, the reduced duty-cycle frequency (f+) is 37.2 and 38.8, which generates a stabilized vortex pattern that reattaches the separated flow and suppresses shear-layer fluctuations. (2) For A°/c = 0.75 and 1.00, the GA converges the f+ to 4.4 and 5.6, which produces an intermixing vortex pattern that dissipates massive detached vortices into smaller, surface-attached structures. Concurrently, the optimal actuator location shifts systematically upstream from x/c = 0.045 to 0.015 with increasing A°/c, targeting progressively earlier separation onset. This upstream placement ensures the induced flow interacts with the incipient shear layer, suppressing DSV formation through enhanced mixing and momentum entrainment. These controlled flow patterns recover the boundary layer, reduce vortex circulation and shear-layer angle, and enhance the lift-to-drag ratio of the plunging airfoil.