The integration of thermal hydraulics (CFD) and finite element (FEM) computer codes in liquid and solid mechanics (MULTIPHYSICS)

The main objective of the project is to improve modeling capabilities for Fluid-Structure-Interaction (FSI) systems. The FSI problems are very common in industry, and there is a growing need to develop simulation tools for these problems. An important application in nuclear industry is the structural integrity of nuclear reactor core internals in Design Basis Accident (DBA). The specific case studied in the project is Large Break Loss of Coolant Accident (LBLOCA) and especially the pressure transient, which is caused by the guillotine pipe break. Tools used for the analysis are Computational Fluid Dynamics (CFD) and Finite Element stress and strain Analysis (FEA) codes. An original aim of the project was to study the possibility to develop one numerical model for system geometry with suitable meshing for all physical analysis, including both CFD and FEA modeling. However, quite soon it was noticed that the common meshing would decrease the quality of both analyses too much. The goal was updated to couple the separate CFD and FEA calculations through internal or external interpolation code. The FEA codes used in this work are NASTRAN and ABAQUS. The codes FLUENT and STAR-CD were used in the CFD side. The coupling was made using the internal coupling model ES-FSI of the STAR-CD and external interpolation code MpCCI. Boundary conditions in the pipe break were calculated using system codes.