Assesment of high performance computing for nuclear reactor thermal-hydraulics applications

Over the last decade High Performance Computing (HPC) has become an attractive tool in nuclear safety analysis due to the fast progress in building large computing clusters. In particular, Computational Fluid Dynamics (CFD) technique is recognized as a valuable research tool for the analysis of thermal-hydraulics phenomenon. However, the more advanced the code and the research problem, the time needed to obtain a final results is respectively longer. Therefore, it is important to consider not only computational capabilities but also efficient use of the available resources. The aim of this work is to present technical aspects of scalability of the spectral element code NEK5000 and the feasibility to run a large-scale Direct Numerical Simulation (DNS) using HPC cluster. The paper is divided in two parts: the first one contains a detailed description of Świerk Computing Centre (CIŚ) infrastructure, while the second one is devoted to the genuine and sophisticated performance tests done at CIŚ. The first set of tests checked the scalability of NEK5000 code on the hardware installed at CIŚ. Further tests checked the efficiency of use of the available resources by means of CPU configuration and network configuration options. The efficiency in every case is calculated based on the execution time of a standardized test case.