Simulation of collapse and fragmentation phenomena in a sharp interface Eulerian setting

Sharp interface Eulerian methods are used to develop a technique for handling high speed material dynamics leading to collapse and fragmentation. Two problems are of primary interest, viz. void collapse in energetic materials and fragmentation of solids under impact; in the first case the sharp interface reconnects to itself, while in the second the sharp interface is torn apart. The challenge is to simulate using a sharp interface Eulerian approach through these topological changes and to apply boundary conditions on the immersed interfaces. Level set interface representations are combined with a modified Ghost Fluid Method to solve sharp interface dynamics in the presence of elasto-plastically deforming solid materials. A unified method of populating ghost field is developed using an adaptive least squares approach and demonstrated to be robust for severe interface deformations, including changes in topology. A parallel algorithm is used to enable solutions of large scale problems. The embedded material interfaces undergoing severe deformation while moving at a very high speed are handled efficiently and accurately in a multi-processor setting. Validation exercises, examples and benchmark calculations are presented to demonstrate the accuracy of the approach.