Constraining the amplitude of ablation-driven pressure waves with CFD-assisted image simulations

The pressure and shock waves generated in laser-driven cavitation studies can be too brief or too small for a physical pressure sensor. Instead, the dynamics of the system can be quantified by measuring the velocities of shock waves and bubble interfaces from optical images. This method will have poor accuracy if the optical image is distorted, such as when imaging shock waves in a droplet. Here we report developing accurate ray-tracing image simulations of the pressure waves generated by an X-ray laser in a water drop. The image simulations used the pressure distributions predicted by an experimentally-matched CFD model of the ablation. The simulated images matched the experimental images of the shock waves for two ablation conditions. We also evaluated the precision with which the amplitude of the shock can be constrained using simulated images. Image simulations using scaled pressure distributions displayed wave features with a poorer match to the experiment than the experimentally-matched pressure distribution, showing that image simulations can be used to constrain the measurement of ablation-driven shock amplitudes to ±10 MPa.