NUMERICAL INVESTIGATION OF AN UNSTEADY TYPE IV SHOCK-SHOCK INTERACTION
非定常IV型激波－激波干扰数值模拟研究

Self-sustained unsteady turbulent flow resulting from a IV typed shock-shock interaction is simulated numerically. Full N-S equations implemented with the algebraic Baldwin-Lomax model are solved by using finite volume method, second-order Harten-TVD spatial scheme and second-order Runge-Kutta method. Regular oscillatoins and a periodic structure of dual eddies are observed, which do not exist in steady cases. The peak pressure also oscillates regularly in its value and position, but their variation are very small. Time-averaged wall pressure coefficient and Stanton number distributions appear in good agreement with steady experimental results. From variations of three representative lines in the flow field, the inherent unsteady mechanism and influence factors are then analyzed by studying disturbances propagating in one cycle, and the phases of the structure variation. The disturbances propagate through subsonic areas, shocks and shear layers. Because of different structures having different phases, the disturbances finally result a regular periodic flow field. It shows that the phase difference between two shear layers near the wall, and the length difference between shear layers abuting against the supersonic jet are two facts that influence the flow field significantly.