Numerical Modeling for Laser-Drop Explosions

Project information
Period	January 2023 - December 2025

Laser irradiation can cause high-speed liquid-droplet breakup by forming plasma inside the liquid, leading to its disintegration. X-ray free electron lasers (XFELs) deposit higher energy densities, resulting in ultrafast and violent droplet breakups. Understanding these mechanisms remains challenging. Numerical studies have explored shock-driven explosions of water microdrops using a sharp-interface method, which fails to capture off-center cavitation observed experimentally. Volume-fraction-based methods are better suited for modeling cavitation. A diffuse-interface method has been developed to accurately capture interfaces and model spontaneous cavitation.

The developed discrete-equations method (DEM) extends the Godunov method for multi-phase flow, solving pairwise Riemann problems for phase fluxes and non-conservative coupling terms. Despite its robustness, DEM's interface flow accuracy is hindered by diffusion or restrictive time-step limits. A modified DEM scheme addresses these issues by partitioning Riemann problems and coordinating fluxes to prevent restrictive acoustic waves. This scheme, combined with the THINC reconstruction and positivity-preserving averaging, enhances interface-capturing accuracy.

In this project we aim to extend our high-order compressible flow solver ALPACA to further include phase transitions, crucial for modeling spontaneous cavitation and spallation in laser-induced drop explosions. This involves incorporating physical models for cavitation and refining THINC-based interface sharpening to capture new phase boundaries accurately.