Effect of diagonal expansion ramps On mixing and noise characteristics Of supersonic rectangular jet

Abstract

Understanding supersonic jet mixing has been of substantial newlineimportance in the fields of high-speed aerospace combustion and jet exhaust newlinenoise suppression. High noise levels, over 150 dB are generated by supersonic newlinejet flows from tactical aircraft, rocket motors, and injector nozzles of newlineSCRAMJET engines. These noise levels are serious health and safety concerns newlinefor both ground personnel and vehicle s structural components. The last three newlinedecades have seen many noteworthy findings in achieving faster decay of newlinesupersonic jets using rectangular nozzles. Therefore, jet noise reduction, newlineespecially of non-ideally expanded jets has been a perennial challenge to the newlinefluid dynamic and aero-acoustic research communities. newlineIn the present research work, experimental and computational newlineinvestigations were carried to evaluate the efficacy of expansion ramps on the newlinemixing and acoustic characteristics of a controlled supersonic rectangular jet. newlineA Mach 1.8 rectangular jet issuing from a converging-diverging nozzle of newlineaspect ratio 2:1 is considered as the baseline model for the study. Ramp length newlinealong the divergent portion of the nozzle has been kept constant as 6.5 mm from newlinenozzle exit towards the throat (one-third of divergent portion length) for all newlineexperiments and computations. Studies on the effect of such expansion ramps newlineon decay, spread, and acoustic characteristics of supersonic jets are sparsely newlineavailable in the existing literature. Further, studies on the effect of diagonally newlineplaced expansion ramps on jets issuing from rectangular nozzles have not been newlineattempted by researchers newline