- The validity of the simulation results from computational fluid dynamics (CFD) is 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 requires an improved understanding of the detailed flow structure evolution 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. The fundamental phenomena of fluid flow in rod bundles with spacer grids can be elucidated by using state-of-the-art measurement techniques. This study aims to develop an experimental data base with high spatial and temporal resolution of fluid flow velocity inside a 5 5 rod bundles with spacer grids. The full-field detailed data base is intended to validate CFD codes at various temporal-spatial scales. Measurements are 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 full field velocity vectors and turbulence statistics for a rod bundle under single phase flow conditions. 2009 Elsevier B.V. All rights reserved.