Travelling Bubble Cavitation and Resulting Noise.
PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB
Pagination or Media Count:
Many theories describing cavitation noise model the phenomenon by considering the independent annihilation of cavities in an infinite fluid. Since most practical applications involve cavitation generated by the dynamical action of flow, it is valuable to know how these theories will compare with such experimental data. In this investigation, a Schiebe body is employed as a headform that supports travelling bubble cavitation which is analyzed with regard to the various theories. High-speed films were taken of bubbles collapsing on the headform while the accompanying noise signal was recorded. These results showed rebounds to generate almost as much noise as the initial collapse. By counting the number of noise bursts occurring for given noise level and flow parameters, it was found that the noise energy per bubble varies with the cavitation number as roughly sigma to the -8 power above 10 kHz, but not at all with the free stream flow velocity V sub infinity between 30 and 40 fps. The spectral energy density was observed to be flat, regardless of sigma and V sub infinity, from 10 to 100 kHz. Although maximum bubble radii as functions of sigma and V sub infinity were not adequately measured during this study, it is clear that an understanding of this parameter is critical to any cavitation noise theory.