Validation of Hydriding Models for Solid and Liquid Ejecta in Reactive Media

Results from ejecta experiments performed at Los Alamos National Laboratory show that molten particles ejected from a shocked metal surface show largely varying behavior depending on whether they chemically react with their accepting medium. Those ejected into an inert medium demonstrate expected deceleration behavior with monotonically decreasing velocities at a nearly constant rate. However, those ejected into a reactive, hydrogen-based medium show a staged deceleration phenomenon in recorded velocimetry data. A working hypothesis is that these reacting ejecta particles form hydride shells and the presence of the shell leads to subsequent physical processes which cause the observed non-monotonic decelerations. The specifics of the physical processes which control this phenomenon are mostly unknown and are of interest for developing accurate models for simulating the trajectories of the metal particles after ejection. This work first describes developed, point-particle based models for the hydride shell intended to simulate both shedding of nanoparticles from the evolving hydride shell surface along with any phase changes which may be occurring in the shell. The coupling of the modeled mass and energy transfer of the shed particles to the surrounding fluid flow through a dusty gas approximation is also described. Lastly, recent simulation efforts which compare the created ejecta framework against experimental data encompassing inert and reactive ejecta, both solid and liquid in nature, are discussed to assess the accuracy and potential pitfalls of the model and its assumptions.