Multi-Scale CFD Simulations of Momentum and Buoyancy Driven Flows in Nuclear Reactor Systems

The present study focuses on the validation of the multi-scale CFD simulations for the nuclear systems. It is mainly divided into the three applications; First is the validation analysis of the large scale PANDA experiment for the containment safety, Second is mainly focused on the international benchmark project GEMIX in order to quantify the level of the involved uncertainty in CFD simulations, due to the turbulence modeling, and third is the validation study for the PWR 5x5 bundle with mixing vane to investigate and validate flow structures at the downstream of the mixing vane. The first part of the work being proposed is to conduct further analysis on the containment safety by using available scale resolved modeling such as LES. In addition to the scale-resolved simulation, available data reduction techniques such as Proper Orthogonal Decomposition is applied to extract coherent turbulent structures in the flow. The second part, in order to quantify the level of the involved uncertainty in CFD simulations, benchmark activities have been conducted by various groups at different scales. The GEMIX test facility was used to develop benchmark data. The facility involves the mixing of two fluids that are initially separated. One of the two streams is water with sugar dissolved and other stream is distilled water, which produces density differences between the two streams. Velocity fields and concentration measurements were acquired. The velocity fields were acquired using PIV and concentrations of each fluid were acquired using LIF. The activity provided the opportunity to quantify the validation study for CFD. The third part, the single-phase hydraulic problem presented involves the steadystate turbulent flow field modelling and resolution around a scaled PWR mixing vane grid tested by Texas A&M University. The most vital contribution of this part will be the contribution to the literature with high resolution direct 3-D experimental and computational results comparison. Additionally, validated numerical results is processed to create higher order turbulent statistics database to help turbulence modeling for the subchannel analysis and contribute to further verification and validation studies. POD and DMD techniques are used to extract coherent turbulent structures numerically