Three dimensional sharp interface Eulerian computations of multi-material flows

This work presents a three-dimensional, Eulerian, sharp interface, Cartesian grid- technique for simulating the response of elasto-plastic solid materials to hypervelocity impact, shocks and detonations. The mass, momentum and energy equations are solved along with evolution equations of deviatoric stress and plastic strain using a higher order shock capturing ENO scheme. Material deformation occurs with accompanying nonlinear stress wave propagation; in the Eulerian framework the boundaries of the deforming material are tracked in a sharp fashion using level sets and the conditions on the boundaries are applied by suitable modifications of a ghost fluid approach. The dilatational response of material is modeled using the Mie-Gruneisen equation of state and the Johnson-Cook model is employed to characterize the material response due to rate-dependent plastic deformation. This work deals with modification of deviatoric stress ghost state so that physically correct boundary conditions can be applied at material interfaces. An efficient parallel algorithm is used to handle computationally intensive three-dimensional problems. The computer code developed in this work is then used to solve several problems in high speed impact phenomena. Numerous examples pertaining to impact, penetration, void collapse and fragmentation phenomena are presented along with careful benchmarking to establish the validity, accuracy and versatility of the approach. A detailed analysis of the response of a porous energetic material exposed to severe loadings (that are likely to trigger explosion) is studied using the established framework. Important insights into the effect of porosity on the material response to imposed shock loadings are obtained.