Influence of Large-Scale Coherent Structures on Lift Loss in Supersonic Impinging Jets*

Supersonic impinging jets are essential components of Short Take-Off and Vertical Landing (STOVL) aircraft operation. These impinging jets are prone to resonance via a feedback mechanism, yielding highly unsteady flowfields characterized by large-scale coherent structures. These coherent structures are associated with the generation of intense acoustic waves, leading to loud noise. Concurrently, these high-speed jets entrain the ambient air, forming a region of negative pressure beneath the fuselage that prompts a loss of lift. This induced lift loss can be significantly augmented in the presence of large-scale coherent structures. The present study aims to explore the relationship between lift loss and noise using a supersonic round jet (Mach 1.5). The lift loss is quantified by pressure measurements beneath a lift plate simulating a fuselage. The lift loss measurements are performed simultaneously with acoustic measurements over a range of impingement distances, encompassing cases with both microjet actuation and uncontrolled jet conditions. Evaluation of the results is facilitated through schlieren flow visualization and Particle Image Velocimetry (PIV) at selected impingement distances.