高性能军用飞机实用喷嘴喷射的流动和声学研究

This research project examines supersonic jets from nozzles representative of the practical variable-geometry convergent-divergent nozzles used on high-performance military aircraft. The nozzles employed have conical convergent sections, sharp throats and conical divergent sections. Nozzles with design Mach numbers of 1.3, 1.5, 1.56 and 1.65 are tested and the flow and acoustics examined. Such nozzles are found to produce a double-diamond shock structure consisting of two overlapping sets of shock cells, one cast from the nozzle lip and one cast from the nozzle throat. These nozzles are found to produce no shock-free condition at or near the design condition. As a result they produce shockassociated noise at all supersonic conditions. The shock cell spacing, broad-band shock-associated noise peak frequency and screech frequency all match those of more traditional nearly isentropic convergentdivergent nozzles.