Three-dimensional fluid-structure coupling in transient analysis

Abstract

The numerical simulation of nonlinear, transient fluid-structure interactions (FSI) is a current area of concern by researchers in various fields, including the field of nuclear reactor safety. This paper primarily discusses the formulation used in an algorithm that couples three-dimensional hydrodynamic and structural domains. Here, both the fluid and structure are discretized using finite elements. The semi-discretized equations of motion are solved using an explicit temporal integrator. Coupling is accomplished by satisfying interface mechanics. The structure imposes kinematic constraints to the moving fluid boundary, and the fluid in turn provides an external loading on the structure. At each interface node, normals are computed from the nodal basis functions of only the hydrodynamic nodes. By defining the interface normal in this manner, it becomes independent of the type of structural boundary (i.e. shell, plate, continuum, etc.) and thus makes this aspect of the coupling independent of the structure type. A penalty type gap-impact element is developed to model the impact region between the fluid and structure. Results for several problems are presented and these include a comparison between analytical results for a FSI problem and numerical predictions.