open access

https://hdl.handle.net/2115/14913

Strongly nonlinear waves and streaming in the near field of a circular piston

英語

1996-06-01

The Journal of the Acoustical Society of America

99(6)

3353-3372

The propagation of nonlinear waves radiated by a circular piston mounted in an infinite plane rigid wall is numerically studied without the restriction of weak nonlinearity, in the case that the radius of piston is comparable with a typical wavelength of the radiated wave. The piston executes harmonic oscillations and the wave is thereby emitted into an ideal gas of semi-infinite extent, in which the dissipation effect is supposed to be negligible everywhere except for the discontinuous shock front. The wave phenomenon in the near field caused by the strongly nonlinear effect combined with the diffraction effect is clarified by solving the Euler equations with the upwind finite difference scheme. Owing to the strong nonlinearity, not only the waves emitted directly from the piston face but also the diffraction waves from the edge of the source are distorted and developed into the shock waves. This can lead to a multiple interference of shock waves in the near field. The separation phenomenon at the edge is also shown. Another remarkable phenomenon is the excitation of strong streaming (a mean mass flow), which forms a vortex-ring-like flow pattern and rarefies the gas near the source during the several periods of oscillation of the piston. By using a regular perturbation expansion, acoustic streaming in the weakly nonlinear problem is also analyzed, which does not show such a vortex-ring-like flow pattern and never rarefies the gas near the source. ©1996 Acoustical Society of America.

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Copyright 1996, Acoustical Society of America. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the Acoustical Society of America.

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