In general, the numerical simulation is a powerful tool for research as well as for industial engineering. This study allows us to explore a new calculation code NSMB and the parallel computing on supercomputers. We have also studied the Landau theory, different PSD estimate method as well as the POD method in order to calculate the Strouhal number, to observe the phomenema of Von Kármán vortex as well as the Kelvin Helmholtz instability. Future research would be the dimensioning / design of the cylinders bundle in the nuclear reactor based on high fidelity modeling and reduced order/ POD based modeling (BARESAFE ANR project).