Numerical Investigation of a Multiphase-Based Closure Relation for Macroscale Energetics Modeling

Production-level hydrocodes are routinely used to predict and assess the performance of energetic material systems at engineering scales. The fundamental physics utilizes the reactive Euler equations, together with an equation of state for the energetic mixture and a reaction rate law that describes the chemical reaction kinetics. Collectively, the latter are referred to as a reactive flow model. The governing equation set requires an additional expression, known as a closure model, for a complete description of the system. An appropriate physical basis of the closure model, however, remains an open question. Previous efforts have shown that the commonly-used closures included in hydrocodes show little variance in predicted pressure and particle velocity fields within the material reaction zone, while density and temperature profiles can differ significantly. For pressure-dependent reaction rates suitable for legacy materials, this is likely not a significant issue. However, advanced reactive flow models developed for novel energetic materials, which utilize temperature and entropy, may produce very different predictions. Consequently, the development of a physics-informed closure model is crucial in ensuring the accuracy of hydrocode predictions for novel materials. In this work, we show how a multiphase model description may be used to derive such a closure relation. This approach has the advantage of utilizing specific, well-characterized transport processes among the mixture components, rather than relying on the heuristic description that is traditionally used. We also show results of a preliminary parametric analysis for one-dimensional flow to investigate sensitivity of the reaction zone profiles.