摘要:
基于可压缩流体力学基本理论,通过边界积分方程,采用不同表面压力模型,求解空泡在计及可压缩性的涡流场中的运动规律;通过表面离散及坐标变换,采用Kirchhoff动边界积分方程,将空泡表面视为运动变形边界,作为直接噪声源,获得涡流场中空泡运动产生的时域声压分布;分析了涡流场参数对空泡运动规律及声辐射特性的影响.研究结果表明:计及流场可压缩性,空泡的脉动幅度会随时间减弱,辐射声压幅值随之减小;空泡在涡流场中会发生延展、颈缩、撕裂,并在撕裂后子空泡中形成射流;当流场中的压力减小时,空泡运动过程中的最大半径与撕裂前的最大长度逐渐增加,且当流场中压力较小时,空泡撕裂时形成的子空泡增多;空泡辐射声压的指向性较弱,撕裂会使辐射声压产生突变,形成极大峰值;随着涡通量的增大或空泡数的减小,空泡脉动周期及其诱导的辐射声压波动周期随之延长,辐射声压峰值逐渐滞后并减小.本文结果旨在为涡流场中空泡运动规律及声辐射特性的相关研究提供参考.
关键词:
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可压缩
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涡流场
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空泡
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声辐射
Abstract:
Based on the compressible fluid theory, the boundary integral equation is used to solve the motion law of cavitation in vortex flow within different surface pressure models. The time-domain sound pressure characteristics induced by cavitation in vortex field are obtained by the moving surface Kirchhoff formulation. With the surface discretion and coordinate transformation, the cavitation surfaces are treated as the moving deformable boundary and the acoustic source directly. The influence of vortex field parameters on motion and radiation of cavitation is analyzed. Results show that with the consideration of compression, the amplitude of cavitation’s pulsation as well as the sound pressure will be decreased. In the vortex fluid, cavitation will be extended, necked and splitted, and may generate a jet in sub-bubbles. While the pressure is reduced in the fluid field, the maximum radius and length before splitting of the cavitation will be enlarged. The number of sub-bubbles will increase when the pressure is small in the fluid field. The directive property of cavitation is weak. And the splitting of cavitation will generate a great peak value of sound pressure. With the increase in vortex flux or the decrease in the cavity number, the period of the cavitation oscillation and its radiation sound pressure are elongated, and the peak of sound pressure is retarded and reduced. The results in this paper could be used as the reference data for the research about the motion and sound radiation characteristics of cavitation in vortex fluid.
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