Acoustic and hydrodynamic response of an annular cascade to inflow disturbances in swirling flows

A model is developed for the interaction of high frequency inflow disturbances with an annular cascade in swirling flows. The computational domain is decomposed into inner and outer subdomains. The outer subdomain scales with the radius of the duct R and the high frequency approximation is used to simplify the governing equations. The inner subdomain scales with the blade chord c ≪ R, and the mean flow variation due to the blade geometry has significant effects on the solution. The numerical results show that for swirling mean flows, as the rotor-stator spacing increases the unsteady blade pressure and the level of acoustic radiation are first reduced. However, further increasing the spacing to more than 2-3 chord lengths produces no significant change. The spanwise variation of the swirl angle (blade twist) has significant effects on the spanwise unsteady lift distribution and propagating acoustic pressure. Spanwise modulation of the incident gust reduces the unsteady lift considerably.