Comparison of Hydriding Models to Experiments for Liquid Metal Ejecta in Reactive Media

Experiments performed at Los Alamos National Laboratory show that molten particles ejected from a shocked metal surface demonstrate unexpected transport behavior depending on their ability to chemically react with their accepting medium. Inert ejected particles demonstrate expected, near-constant deceleration and temperature equilibration behaviors. However, molten particles ejected into a reactive, hydrogen-based environment are believed to form hydride shells during transport and demonstrate both a staged deceleration behavior and an apparent temperature plateau in experimental measurements. The current hypothesis is that the presence and growth of the hydride shells leads to a subsequent physical process which is the cause of the observed anomalies in the velocity and temperature data. Details of these processes are still not well understood and are needed for accurate models for the transport of ejected metal particles. This work describes a point-particle based model meant to capture the effects of shedding of nanometer scale flakes from the hydride shell due to stresses from expansion as well as phase change of the shells. This framework, which is fully coupled to the background fluid flow for both mass and energy transfer, is utilized in a simulation effort to compare with experimental data which contains both inert and reactive ejecta. The accuracy and potential pitfalls of the model and its assumptions are discussed as well as additional physics improvements to help address the pitfalls.