I.V.Vovk, V.T.Grinchenko, Yu.M.Dudzinskii On possible self-oscillation mechanism in hydrodynamic jet radiators with developed cavitation |
Acoustic bulletin, Vol. 11 ¹ 2, (2008) |
| The paper deals with analyzing in detail the operation of a counter-flow hydrodynamic jet radiator of the sound with a developed cavitation inside the jet-shell. The basic hydrodynamic and acoustic properties of the devise are discussed. A hypothesis is offered, that illustrates the possible physical mechanism for generating self-oscillations of radiator's jet-shell. The simplest acoustic model of the jet-shell is proposed and the boundary problem on sound radiation by it is solved. The analysis of the obtained solution allows the conclusion that a specific resonant system forms inside radiator'ss working zone. The mentioned system consists of the internal compressible cavitation environment, jet-shell itself and external added mass of the liquid and provides the acoustic feed-back, imposing jet-shell's self-oscillations with stable frequency. It is shown that the paradoxical reduction of radiated sound frequency with growing jet speed in the nozzle obtained in the experiments is related with the increasing compressibility of the internal cavitation environment due to increasing share of vapor-gas microbubbles in it. The quantitative estimations of compressibility, density and sound velocity in the internal cavitation domain are offered. In particular, it is shown that the last value is essentially lower than sound velocity in the external liquid surrounding the jet-shell. |
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KEY WORDS: a hydrodynamic acoustic radiator, cavitating medium, resonant system, effective mass, effective elasticity |
| TEXT LANGUAGE: Russian |