Experimental study of a simplified 3 × 3 rod bundle using DPTV

Abstract Computational fluid dynamics (CFD) has evolved over the last years as an important tool for the simulation and prediction of rod bundles in plant components under various scenarios, contributing to the continuing improvement of performance and safety of nuclear power plants. However, these tools must be validated and verified in order to assure, with enough confidence, the reliability and quality of CFD predictions. The present work focuses in the basic study and a benchmark case of rod bundles using a top-bench experimental set up. The experimental set-up provides complete optical access to the test section by using a matching refractive index between the liquid flow, rods and flow envelope. Dynamic particle tracking velocimetry (DPTV) was used to measure the time resolved velocity fields in the rod bundle. Experimental turbulence parameters and main flow characteristics are presented in this work. This study seeks to provide a basic yet enough comprehensive benchmark case for CFD under single-phase conditions. The geometry associated with the bundle problem has been simplified in order to provide high quality data (high temporal and spatial resolution) in order to directly compare with CFD results. The measurement uncertainties in these experiments are discussed and evaluated yielding an uncertainty of 11% in the axial and lateral velocity components of the measured velocity vectors. This work is a collaborative effort between Texas A&M University and the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) Institute in Germany.