A computational framework for the simulation of high‐speed multi‐material fluid–structure interaction problems with dynamic fracture

Abstract

A robust computational framework for the solution of fluid-structure interaction problems characterized by compressible flows and highly nonlinear structures undergoing pressure-induced dynamic fracture is presented. This framework is based on the finite volume method with exact Riemann solvers for the solution of multi-material problems. It couples a Eulerian, finite volume-based computational approach for solving flow problems with a Lagrangian, finite element-based computational approach for solving structural dynamics and solid mechanics problems. Most importantly, it enforces the governing fluid-structure transmission conditions by solving local, one-dimensional, fluid-structure Riemann problems at evolving structural interfaces, which are embedded in the fluid mesh. A generic, comprehensive, and yet effective approach for representing a fractured fluid-structure interface is also presented. This approach, which is applicable to several finite element-based fracture methods including inter-element fracture and remeshing techniques, is applied here to incorporate in the proposed framework two different and popular approaches for computational fracture in a seamless manner: the extended FEM and the element deletion method. Finally, the proposed embedded boundary computational framework for the solution of highly nonlinear fluid-structure interaction problems with dynamic fracture is demonstrated for one academic and three realistic applications characterized by detonations, shocks, large pressure, and density jumps across material interfaces, dynamic fracture, flow seepage through narrow cracks, and structural fragmentation. Correlations with experimental results, when available, are also reported and discussed. For all four considered applications, the relative merits of the extended FEM and element deletion method for computational fracture are also contrasted and discussed. . Multi-fluid and multi-material flows are typically characterized by the presence in well-defined regions of space of two or more fluids with different material properties. Multi-phase flows feature different phases or mixtures of fluids. For the purpose of this paper, all three labels are unified under the name 'multi-material', as this label is most suitable for describing the additional structural aspect of the aforementioned coupled problems.The development of a computational framework for the simulation of highly nonlinear, highspeed, multi-material FSI problems with dynamic fracture is a formidable challenge. It requires accounting for all possible interactions of all fluid and structural subsystems and therefore tracking all fluid-fluid and fluid-structure interfaces. It also necessitates the proper discretization of the governing flow equations across fluid-fluid interfaces involving different equations of state (EOSs) and high density jumps and fluid-structure interfaces undergoing topological changes. The development of such a computational framework also calls for the modeling of geometrical nonlinearities, material failure a...

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