G.A.Voropaev, A.V.Voskoboinick, V.A.Voskoboinick, V.T.Grinchenko, S.A.Isaev, N.V.Rozumnyuk Sources of pseudosound pressure fluctuations in the flow over the spherical dimple |
Acoustic bulletin, Vol. 11 ¹ 3, (2008) |
| The paper deals with theoretical and experimental investigation results on characteristics of pseudosound pressure oscillations caused by interaction of the flow and sound field inside the three-dimensional spherical dimple. The results of numerical and physical simulation of vortex movement features inside the dimple and in its near wake are shown. The symmetric and asymmetric large-scale vortical systems have been found inside the dimple, their existence depending on flow regime. Their location and outbreak periodicity are specified. The evolution of tornado-like vortices is subjected to trigger mechanism resulting in the occurrence of low-frequency modulating transversal oscillations of vortex motion inside the dimple. The high-Q discrete peaks are discovered in the spectra of pressure and velocity fluctuations, that correspond to frequency of vortex systems rotation inside the dimple, their outbreak frequency, wake mode frequency of vortical motion oscillations in the dimple, caused by the hydrodynamical resonance, and shear layer self-oscillation frequency, corresponding to the acoustic resonance. The shape and dimensions of the quasi-stable large-scale vortex structures, their generation regions and development stages have been specified. The instantaneous and average characteristics of pseudosound pressure fluctuations for vortical movement inside the dimple and in its near wake are different because of nonlinear interaction of vortical structures with each other and with streamlined surface. |
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KEY WORDS: the flowing, pseudosound, a tornado-like vortex, the wake mode, shear layer self-oscillations, feedback |
| TEXT LANGUAGE: Russian |