Journal of Fluid Science and Technology
Online ISSN : 1880-5558
ISSN-L : 1880-5558
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Experimental and Theoretical Investigations of Edge Tones in High Speed Jets
Mohammed K. IBRAHIM
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2013 Volume 8 Issue 1 Pages 1-19

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Abstract

Experimental and theoretical investigations of the high speed jets impinge on a wedge-shaped edge have been conducted. Sonic circular and square jets of the same hydraulic diameter are examined in the present study. Edge-tones produced due to a wedge-shaped edge having different angles, specifically, 10°, 20°, 60° and 180°, have been investigated. Experiments reveal that several instability modes exist simultaneously in the microphone-captured acoustic signal. The minimum breadth is defined as the minimum distance of the edge from the nozzle exist for the first tone to be generated. Experiments showed that at small edge angle, the minimum breadth is approximately half of its equivalent two-dimension case. Semi-empirical frequency formula for the dominant tone is proposed based on the present experimental data for small edge angles. The theoretical results based on the vortex-sheet model proposed by Tam and Ahuja(1) showed that both helical and axisymmetric stability modes exist during jet impingement. The dominant tone usually has helical stability mode which is the well known edge-tone. Other tones are known as impinging-tones in the literatures and have axisymmetric stability modes. Finally, it has been shown that the experimentally obtained mean Strouhal numbers for helical and axisymmetric modes show good agreement with the Strouhal number of the least dispersive wave of the same mode calculated at various Mach numbers.

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© 2013 by The Japan Society of Mechanical Engineers
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