Numerical investigation of dynamic starting characteristics for 2-D variable geometry inlet based on overset grid

The inlet is one of the important components of air-breathing scramjet engines which is crucial to the performance of the whole propulsion system. In the flight of hypersonic vehicles, the variable geometry inlet is the focus of attention because of its good aerodynamic performance in a wide range of Mach numbers. The numerical simulation of variable geometry inlet with rotating cowl is performed by solving Reynolds Averaged Navier-Stokes (RANS) equations with dynamic overset method. The highly hole-cutting method and search technique of overset grid are adopted for dynamic starting characteristics simulation. The effect on aerodynamic characteristics of internal contraction ratio variations caused by cowl rotation is investigated. The influences of oscillation parameters on the hysteresis effect are investigated and the evolution procedure of separation bubble is presented. For the cowl rotating with constant angular velocity, numerical results show the inlet with rotating cowl can help to enhance the self-starting ability. The value of unstarting convergence angle increase with the increasing of reduced angular velocity. For the cowl rotating with cyclic motion, an abrupt rise and decrease exists in the hysteresis loop of inlet performance parameters when unstarting and restating occur. Moreover, the effect of oscillation frequency on unstarting/restating convergence angle is discussed.