Bubble dynamics and resulting noise from traveling bubble cavitation

The acoustic noise spectrum associated with traveling bubble cavitation on a Schiebe headform in a variable pressure water tunnel was measured over the 2.5 to 80 kHz frequency range. Bubble dynamics were observed through video taping and the nuclei distribution was obtained holographically. Observed noise spectra showed that low frequency noise can be modeled by incompressible theory. High frequency noise, apparently resulting from a shock wave, can be modeled by compressible theory. The spectrum was seen to shift toward lower frequencies than predicted possibly due to axisymmetric bubble collapse. The spectral energy per bubble was experimentally derived and was found to be a reasonable approximation to that predicted by incompressible theory over the cavitation number range tested. The collapse peak pressure amplitude distribution, the maximum bubble radius distribution and the nuclei distribution were all found to be lognormal.