In this study, we investigate active feedback control of separated flows around NACA0015 airfoil using a Dielectric Barrier Discharge Plasma Actuator (DBDPA) trained via deep reinforcement learning (DRL) in a 3D CFD environment. A deep neural network-based controller with an Attention Branch Network (ABN) structure was trained using Ape-X DQN, enabling dynamic selection of burst frequencies for DBDPA actuation. Compared to predetermined control strategies, the trained controller achieved a higher lift-to-drag ratio by actively adapting to unsteady separation dynamics. Attention maps generated by ABN revealed that the controller focused on key flow features such as separation zones, leading edge vortex shedding, and low-pressure regions near the leading edge, providing interpretable insights into its decision-making process. These findings contribute to the understanding of separation control mechanisms and offer design guidelines for effective sensor placement in practical feedback control systems.
Takada et al. (Wed,) studied this question.