軸対称噴流-有限長直管の自励振動現象

概要

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An experimental investigation has been carried out on the sound resonance associated with the circular pipe of finite length, which is positioned coaxially downstream of a round free jet. Self-sustained oscillations arises due to the impingement of the free shear layer on the pipe's leading edge, and this results in the periodic production of discrete ring vortices in the jet. The predominant frequency of oscillation is found to vary intrinsically with the position of the pipe's leading edge as in the case of the circular ring, in which several modal stages of oscillation have been observed previously. However, when this intrinsic predominant frequency approaches the first or higher eigen-frequencies of the pipe, sound resonance between these two frequency components occurs. Thus, the predominant frequency and the distance between the nozzle exit and the pipe's leading edge, when non-dimensionalized by the initial momentum thickness of the shear layer and the nozzle-exit velocity, should be the only parameters describing these sound resonance phenomena. In addition, the sound power level of the resonance increases nearly in proportion to the sixth power of the jet velocity.
一般社団法人日本機械学会の論文
1987-10-25