TY - JOUR
AU - Sridhar, B. T. N.
AB - The effect of expansion ramps on the acoustic behavior of a supersonic rectangular jet (AR = 2) is studied and compared to a plain rectangular jet. Unheated air jets are issued from converging–diverging nozzles which are operated at Mach number 1.8, Reynolds number (based on equivalent diameter) 1.86×105\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$1.86 \times 10^{5}$$\end{document}, and at three different inlet total pressures corresponding to over, optimum and underexpansion levels. A plain rectangular nozzle is considered as the baseline model; two separate nozzles with expansion ramps cut at the diagonal ends on major and minor internal surfaces are considered for the investigation. These expansion ramps are intended to cause a Prandtl–Meyer expansion near the nozzle exit and together the diagonal arrangement of ramps induces vorticity to the jet in addition to the corner vortices emanating from the rectangular nozzle exit section. To understand the jet acoustic behavior and directivity of noise, far-field microphone measurements are performed in planes that are downstream, sideline, and upstream to the nozzle exit. The noise results obtained reveal a highly asymmetric nature in the sound field. Compared to the plain rectangular jet, the screech noise has been observed to be lesser in jet from the nozzle with ramps on the major sides. Acoustic benefit in terms of overall sound pressure levels has been exhibited by both ramped jets, especially for the overexpanded condition in all directions. For optimum expansion level, the plain rectangular jet radiated lesser noise levels in all directions. Of all cases studied, minor side ramps are observed to be the loudest at underexpansion conditions in upstream directions. With the obtained results, the major side ramps are observed to act as effective screech noise suppressors at all expansion levels. Both ramped jets have resulted in reduced overall noise levels (in comparison with the plain rectangular jet) at overexpansion level, with minor side ramps performing better.
TI - Acoustic characteristics of supersonic rectangular jets issuing from nozzles with diagonal expansion ramps
JO - Journal of the Brazilian Society of Mechanical Sciences and Engineering
DO - 10.1007/s40430-021-03286-w
DA - 2021-12-01
UR - https://www.deepdyve.com/lp/springer-journals/acoustic-characteristics-of-supersonic-rectangular-jets-issuing-from-eXeDo6f155
VL - 43
IS - 12
DP - DeepDyve
ER -