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

In this article, we study a large-break loss of coolant accident (LBLOCA) where a guillotine break of one of the main coolant pipes occurs near the reactor pressure vessel (RPV). This initiates a pressure wave which propagates inside the RPV. The simulation of bidirectional fluid-structure interaction phenomena has been found important for accurate prediction of the resulting deformation and loads. In this article, fully coupled simulation results are validated against the German HDR (Heißdampfreaktor) experiments. The computational fluid dynamic (CFD) software Fluent and Star-CD are applied to modeling of three-dimensional, viscous, turbulent fluid flow. The MpCCI code is used for bidirectional coupling of the CFD simulation to the structural solver Abaqus. Pressure boundary condition at the pipe break is obtained in a two-phase simulation with the system code APROS. Comparisons are made for break mass flow, wall pressure, displacement and strain. The simulation results follow the experimental data fairly well. The sensitivity of the results to pressure boundary condition and water temperature is studied. In addition, the necessity of using bidirectional coupling instead of one-way pressure mapping is demonstrated.