Abstract
THIS paper reports the results of an experimental investigation on edge tones generated with a high-speed subsonic air jet-issuing from a rectangular nozzle and impinging on a wedge shaped edge. Experiments were also made to determine the influence of these tones on the mixing of multiple rectangular jets. For exit Mach numbers ranging from 0,2 to 1.0, the minimum breadth required for a tone to be generated increases linearly with Mach number. At distances of the wedge beyond the minimum breadth, the narrow-band spectrum of the near field pressure signals indicate the simultaneous existence of several discrete frequencies, and the amplitude dominant frequencies show different stages. Improved mixing of the multiple jets has been observed when a wedge is placed in one of them. Contents Several experimental studies aimed at understanding the fluid mechanics underlying edge tone generation have been carried out over a period of time at Stanford University. A description of the main features of the edge tone phenomenon and a review of the various experimental and analytical investigations were given by Karamcheti et al.1 The discussion was mainly concerned with the results of experiments on an incompressible jet having a parabolic-type exit mean velocity profile. The main purpose of this paper is to present and discuss the results of experiments on edge tones generated with a compressible subsonic air jet issuing from a rectangular nozzle having a top hat mean exit velocity profile and impinging on a wedge shaped edge. As part of an ongoing program to study the mixing processes of single and multiple rectangular jets, we are interested in a mechanism which can enhance the mixing of multiple jets. As a result, an attempt has been made to study qualitatively the mixing processes of multiple jets with a wedge present in one of them. The main parameters governing the problem are the Mach number M and Reynolds number Re of the jet near the exit, the state of the flow at the exit of the nozzle, the geometry and disposition of the wedge with respect to the nozzle exit, and the condition of the ambient medium into which the jet is issuing. In the present investigation, the exit Mach number varies from 0.2 to 1.0. The Reynolds number employed is based on the width D (small dimension) of the nozzle and is given by Re=MaD/v, where a and v are the speed of sound
Published Version
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