Newly proposed Method of Pressure Measurement by Tracking Particles for Underwater Micro Shock Waves

This paper describes a novel method for pressure measurements of underwater micro shock waves induced by pulse laser. The underwater shock waves are measured by a hydrophone in general. However, it is difficult to measure the pressure of the micro shock wave accurately because its active area is smaller than the sensitive area of the hydrophone. This research proposed methods applying particle tracking velocimetry as the measurement for the micro shock waves. The pressure of the shock wave was calculated from two types of calculation processes with different hypotheses for the change of particle velocity. Method 1 assumed that the velocity of the particle receiving the shock waves decelerates exponentially, and method 2 assumed that the velocity decelerates linearly. As the result of method 1, the pressure at the laser-focal area was calculated to be 28.92 MPa which was higher than the pressure estimated from results measured by hydrophone. Conversely, the pressure at the laser-focal area was calculated to be 7.02 MPa from method 2, which was in the same order as the estimated pressure. From these experiments, it was possible that the proposed pressure measurement applying PTV could be applied to the measurement pressure of micro shock waves.