Non-intrusive experimental investigation of flow behavior inside a 5X5 rod bundle with spacer grids using PIV and MIR

The validity of the simulation results from Computational Fluid Dynamics (CFD) are still under scrutiny. Some existing CFD closure models for complex flow produce results that are generally recognized as being inaccurate. Development of improved models for complex flow simulation require an improved understanding of the detailed flow structure evolution along with dynamic interaction of the flow multi-scales. Thus, the goal of this work is to contribute to a better understanding of presupposed and existent events that could affect the safety of nuclear power plants by using state-of-the-art measurement techniques that may elucidate the fundamental physics of fluid flow in rod bundles with spacer grids. In particular, this work aims to develop an experimental data base with high spatial and temporal resolution of flow measurements inside a 5x5 rod bundles with spacer grids. The full-field detailed data base is intended to validate CFD codes at various temporal-spatial scales. Measurements were carried out using Dynamic Particle Image Velocimetry (DPIV) technique inside an optically transparent rod bundle utilizing the Matching Index of Refraction (MIR) approach. This work presents results showing full field velocity vectors and turbulence statistics for the bundle under single phase flow conditions.