A.V.Voskoboinick, V.A.Voskoboinick Sources of resonance modes of oscillations inside the streamlined hemispherical cavity |
Acoustic bulletin, Vol. 10 ¹ 4, (2007) |
| The paper deals with experimental studying of generation of resonant oscillation modes caused by interaction of hydrodynamic and hydroacoustic phenomena inside the three-dimensional hemispherical cavity. The results of visual investigation of vortical motion features are presented both for the cavity inside, and its vicinity. Depending on flow regime, the symmetric and asymmetric large-scale vortex systems are found inside the cavity. Their location and periodicity of separation are pointed out. The hot-wire measurements of mean value and fluctuations of streamwise velocity and crosswise vorticity profiles show the existence of regions of acceleration and deceleration of the vortex flow, zones of the reverse and circulating flows inside the three-dimensional cavity. The discrete high-quality peaks in four frequency ranges are found in the spectra of velocity fluctuations. They correspond to rotating frequency of vortex systems inside the cavity; their separation frequency; wake mode frequency of oscillations of cavity vortical motion, caused by a hydrodynamic resonance, and self-oscillation frequency inside the cavity, that forms the second Rossiter shear layer mode of self-sustained oscillations (the letter correspond to a hydroacoustic resonance). Form and sizes of quasi-stable large-scale vortex structures, regions of their origin and development stages are pointed out. |
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KEY WORDS: streamlining, hemispherical cavity, thermoanemometer, boundary layer, vortex structures |
| TEXT LANGUAGE: Russian |