摘要：

This paper describes a joint experimental and computational study of the flowfield and acoustics of conical convergent divergent nozzles such as those found on high-performance military aircraft. The influence of chevrons on a nozzle with an area ratio corresponding to a design Mach number of 1.5 (design pressure ratio of 3.67) is examined. The nozzle is tested at its design condition, at overexpanded conditions with pressure ratios of 2.5, 3.0, and 3.5 and at underexpanded conditions with pressure ratios of 4.0, 4.5, and 5.0. Each case is compared to a baseline nozzle at the same condition without chevrons. Shadowgraph images show that chevrons reduce the shock cell spacing. Near-field acoustic measurements show that sources of broadband shock-associated noise move downstream when chevrons are applied. Near-field acoustics also reveal that, for supersonic jets, chevrons produce significant noise near the nozzle exit across the whole range of frequencies. Far-field acoustic measurements show that the application of chevrons reduces screech, broadband shock-associated noise, and mixing noise, except for frequencies above the broadband shock-associated noise peak for overexpanded and perfectly expanded conditions.

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