LAUSR

Abstract An experimental study has been conducted to investigate and compare the effects of bevelled and double-bevelled circular nozzles on supersonic jet screech at a nozzle-pressure-ratio of 5. In particular, near- and far-field microphone measurements and schlieren visualizations were utilized to look into selected acoustic and flow features associated with jet screech radiation. Results show that bevelled nozzles eliminate jet screech by producing asymmetric shock structures and instability waves that are mismatched in phase and amplitude. In contrast, double-bevelled nozzles produce symmetric shock structures and amplify screech intensity, even when jet-mixing effects have been significantly enhanced. It is further observed that amplified jet screech produced by double-bevelled nozzles are highly unsteady and undergo non-periodic and stochastic temporal variations. Last but not least, double-bevelled nozzles also impact significantly upon screech peak noise locations and confer different changes along different measurement planes. The present study demonstrates that not all bevelled-type nozzles are able to mitigate jet screech, with non-optimal designs amplifying it instead.