FSIS: a novel fluid-solid interaction solver for fracturing and fragmenting solids

Transient dynamics of fracturing media has received significant attention in recent years, and a number of simulation approaches have been developed. One of these is the combined finite-discrete element method (FDEM). FDEM produces complex fracture and fragmentation patterns in processes such as blast loads, blasting, impact, mining, and oil exploration. To address a wide range of multi-physics problems, numerous approaches have been undertaken to introduce fluid into the FDEM transient dynamics, ranging from application-specific gas models to more advanced hydraulic fracture processes and biomedical applications. None of these have been satisfactory in terms of robustness, accuracy or computational efficiency. In this work, a completely new explicit fluid solver has been tailor-made and fully integrated (as opposed to coupled) into the combined finite-discrete element method. The solver addresses transient pressure wave propagation in fluid, fluid viscosity, equation of state for the fluid, energy transport, momentum transport, and interaction with the fracturing solid domains, which is done through a novel immersed boundary approach. The solver is based on the governing equations being resolved using different control volume schemes, with discretization errors of either third, second, or first order. The solver is fully explicit and conditionally stable with a time step that is synchronized with the FDEM's time step.