Computational Fluid Dynamics

VTF shell-fluid simulation of water hammer with plate fracture.

For the velocities involved in hypervelocity impact, the stresses encountered by both the projectile and target in the immediate vicinity of the point of impact are greatly in excess of the yield stress of both target and projectile materials. Parts of the configuration are expected to transition undergo solid-liquid-vapor phase transitions, ionization and plasma formation, hydrodynamic instabilities and possibly mixing. In addition, the deformation in the solid phase is expected to involve high-strain rate adiabatic plastic flows with no fracture and fragmentation. These conditions are ideally suited to a fully Eulerian approach that utilizes a fixed mesh but allows for mixed cells wherein solid, fluid and possibly vapor and plasma can coexist and evolve dynamically. We will utilize robust mixed-phase finite volume patch solvers that integrate the dynamic materials models to be developed by the Solid Dynamics group. Our implementation will run several separate Euler solvers simultaneously within the Center’s Virtual Testing Facility, one for each phase. Phase transitions will be handled by a combination of the ghost-fluid/level set method and the closest-point transform. In addition to the expected melting at the time of and following impact, this approach will also handle re-solidification and arbitrary phase transitions across multiple phases including vapor, the vacuum and the expected formation of a mixed plasma phase. With appropriate boundary conditions, this method will also be used for the tracking of free boundaries and collisions, e.g., between the projectile and the target.