On pressure impulse of a laser-induced underwater shock wave

TL;DR

This study investigates the pressure impulse of laser-induced underwater shock waves, revealing that despite asymmetric pressure peaks, the impulse distribution remains symmetric due to multiple spherical shock waves from plasma regions.

Contribution

It provides detailed high-resolution measurements showing the symmetric distribution of pressure impulse despite asymmetric pressure peaks in laser-induced underwater shock waves.

Findings

Pressure impulse distributes symmetrically across various conditions.

Pressure peaks are non-spherically symmetric.

Shock waves originate from multiple point-like plasmas.

Abstract

We experimentally examine a laser-induced underwater shock wave with a special attention to pressure impulse, the time integral of pressure evolution. %total pressure variation associated with the shock wave. Plasma formation, shock-wave expansion, and pressure in water are observed simultaneously using a combined measurement system that obtains high-resolution nanosecond-order image sequences. These detailed measurements reveal a non-spherically-symmetric distribution of pressure peak. In contrast, remarkably, pressure impulse is found to distribute symmetrically for a wide range of experimental parameters even when the shock waves are emitted from an elongated region. The structure is determined to be a collection of multiple spherical shock waves originated from point-like plasmas in the elongated region.