A Review of Dynamic Stall Mitigation Using Active, Passive, and Bio-inspired Flow Control Techniques

Dynamic stall is a highly unsteady aerodynamic problem that restricts the performance of pitching airfoils used in helicopters, wind turbines, and UAVs. Effective suppression of dynamic stall is crucial for improving aerodynamic efficiency, structural stability, and energy output. Several flow techniques have been developed in the past decade to mitigate dynamic stall, but a thorough assessment of their capabilities, limitations and potential remains limited. This review critically analyses current developments in active, conventional passive, and bio-inspired passive techniques. The analysis compares studies on control mechanisms, aerodynamic effectiveness, implementation challenges, and potential applications. The review highlights that active methods allow for greater control but need external power, while passive methods are easier to implement but offer less operational flexibility. Bio-inspired methods are gaining attention because they combine passive operation with naturally inspired flow-control mechanisms. Overall, the literature suggests that no single technique is universally effective for dynamic stall mitigation. Hybrid strategies and application-specific geometric optimization offer strong promise for future applications. The review highlights existing research gaps and future directions for developing application-oriented dynamic stall mitigation strategies.