ANALYSIS OF UNSTARTED SUPERSONIC FLUTTER IN CASCADE BY SEMIACTUATOR DISK THEORY

Unstarted supersonic flutter in a cascade is characterized by the existence of detached bow shock waves ahead of leading edges of the blades. The oscillating cascaded blades accompanied by the detached bow shock waves are analyzed based on the semiactuator disk theory. The effect of the detached bow shock waves on the stability of blade oscillation in a bending mode with interblade phase angle is investigated, in consideration of the pressure wave reflected at the shock wave surface and the vorticity wave and entropy wave generated by the oscillation of the shock wave and blades. The results show that the detached bow shock waves greatly destabilize the blade oscillation in bending mode, and the flutter boundary markedly extends to a high-frequency region.