Three-dimensional numerical simulations of the droplet explosions induced by x-ray laser pulses

In this work, a three-dimensional numerical simulation of droplet explosions induced by x-ray lasers with varying pulse energies is conducted using a recently developed phase-changing sharp-interface method. Overall, the observed droplet morphology and the temporal evolution of diameter expansion show good agreement with previous experimental measurements. Then, the physical mechanisms of droplet deformation, wave dynamics, phase-change effect, and vorticity deposition are analyzed based on the high-resolution numerical data. The expansion of droplet diameter is primarily driven by the cylindrical shock and torus shock. Meanwhile, a retraction phenomenon is observed at the droplet interface due to the negative-pressure wave and the surface tension. During the cavity expansion, its interaction with the torus shock and the negative-pressure region leads to slight deformation of the cavity wall in the central region. In addition, the dynamics of the vortical structures near the droplet poles are studied, and the effect of the laser pulse energy on the droplet expansion and cavity growth is evaluated. Finally, a statistical analysis of the main droplet fragments under different pulse energies is performed. Higher pulse energies generate more fragments due to the formation of additional liquid filaments. The fragment size distribution is evaluated using lognormal, root-normal, and Gamma fits. Lognormal and root-normal fits describe medium-sized droplets well, while the Gamma fit captures larger droplets more effectively.