engleski

Acoustic diagnosis of singing cavitation vortices

The acoustical field generated by the hydrodynamic cavitation is usually random and broad-band. There is, however, a case in which this field has a tonal character. Indeed, as reported by Higuchi, Arndt, and Rogers (J. Fluids Eng., Dec. 1989), and Maines and Arndt (ASME Symp. Cavitation and Multiphase Flow, 1995), cavitating vortices which shed off from a body immersed in a flow may generate a harmonic acoustic signal. Such singing cavitation vortices do not involve vibrations of the cavitating body. The paper will present the results of the parametric analysis of sound generated by the singing vortices produced in a test on a finite-span hydrodynamic profile immersed in a uniform flow in a cavitation tunnel. The case of a continuous development of the vortex through its filling by air was studied in the test. An acoustical diagnosis of the process of oscillations of the cavitating vortex generating the singing will be presented. The issues relevant for the theoretical modeling of the lock-in mechanism are investigated: necessary conditions for the onset and stability of the process, possible influence of the water velocity differing from that through the cavitation number, influence of the vortex energy etc. The relevant peculiarities of the vortex dynamics are revealed. The question if there is a back-influence of the singing on the basic vortex dynamics is considered.

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