Measurement of pressure and tension waves from underwater bubble collapse using a novel pressure bar sensor

Abstract

In order to obtain the stress waveforms of the bubble collapse impact, we chose the pressure bar method with a high-sensitivity laser transducer to record the stress wave on the rod. The pressure bar device has been improved to measure multiple consecutive microsecond-scale impact, while retaining its ability to measure tensile effects. The drop-weight calibration method was adjusted to make the stress pulse width and amplitude of the calibration impact on the same order of magnitude as the test signal. A more practical method for measuring underwater impact, especially tension, was established, compared to multi-layer structure sensors. The collapse processes of spark-generated bubbles at different stand-off distances were discussed. The mechanism of tension waves was analyzed by the comparation of stress waveforms and secondary cavitation phenomena, which would make the cavitation impact mechanism analysis no longer limited to pressure.