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Effect of Mach number on the acoustic field of 2:1 elliptic-slot jet

Published online by Cambridge University Press:  04 July 2016

S. B. Verma  and
E. Rathakrishnan
S. B. Verma
Affiliation:
Department of Aerospace Engineering, Indian Institute of Technology, Kanpur, India
E. Rathakrishnan
Affiliation:
Department of Aerospace Engineering, Indian Institute of Technology, Kanpur, India
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Abstract

The shock-structure and the related acoustic field of underexpanded jets undergoes significant changes as the Mach number Mj is increased. The present investigation is carried out to study the effect of Mach number on an underexpanded 2:1 elliptic-slot jet. Experimental data are presented for fully expanded Mach numbers ranging from 1.3 to 2.0. It is observed that the ‘cross-over’ point at the end of the first cell at low Mach numbers gets replaced by a normal shock at a highly underexpanded condition resulting in the formation of a ‘barrel’ shock along the minor-axis side with a ‘bulb’ shock formed along the major-axis side. The above change in shock structure is accompanied by a related change in the acoustic field. The amplitude of fundamental frequency along the minor-axis side grows with Mj but falls beyond Mj = 1.75. Along the major-axis side, however, the fundamental frequency does not exist at low Mach numbers. It appears at Mj = 1.75 but then falls at Mj = 2.0. The related azimuthal directivity of overall noise levels (OASPL) shows significant changes with Mj.

Type
Research Article
Information
The Aeronautical Journal , Volume 105 , Issue 1043 , January 2001 , pp. 9 - 16
Copyright
Copyright © Royal Aeronautical Society 2001 

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