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In the flight, hypersonic vehicle goes through different kinds of flight status, experiencing various of disturbances. If control system fails to adjust the pose of vehicle, the pitching, yawing and rolling attitude could be transformed or forced to oscillate transiently, then the dynamic of angle-of-attack can not be avoided. It’s a question whether hypersonic inlet would keep start and how the performances change. In this paper, unsteady CFD simulation is performed on 2-D hypersonic inlet at Mach 4.03. Effect of dynamic angle-ofattack on starting characteristic is analyzed. The investigation suggests that: The appearance, development and disappearance of low mach number region near solid wall is affected notablely, which would alter the aerodynamic characteristic of inlet. For the dynamic increasing of angle-of-attack, characteristics of flow field and performances of inlet are significantly altered, unsteady flow field features and the performances are lag behind of the steady case. For the oscillating motion, the value of unstarting angle-of-attack increase and restarting value decrease with the rising of reduced frequencies. It is predicted that when the reduced frequency reaches a critical value, depending on the initial angle-ofattack, the hypersonic inlet would keep start/unstart in the whole circle.

Results of a Particle Image Velocimetry (PIV) experimental study and unsteady simulation about an overexpanded axisymmetric supersonic impinging jet at Ma=2.982 and dimensionless impinging height as Z/D=4 were presented in this paper. Especially, the detailed unsteady phenomena of the global flowfield coherent structures were focused both by PIV experimentally and numerically. The PIV results clearly demonstrated the formation of the shock cell, the stagnation bubble. With the help of the unsteady CFD technique, the unsteady process of the generation of the oblique shock wave and the Mach disk, the propagation of the oblique shock wave and its reflection on the jet shearing layer and the induced expansion wave, then the formation of the shock cell, the presentation of the stagnation bubble, the appearance of the entrainment vortex and its propagation radically towards the outside, were all further clearly revealed. Both the PIV measurements and the CFD results showed the highly unsteady, oscillatory behavior of the impinging jet. All these results are helpful to understand the overexpanded axisymmetric supersonic jet impingement phenomenon.