Benchmark Experiments for Turbulent Mixing in the Scaled-Down Upper Plenum of High-Temperature Gas-Cooled Reactors Under Accident Scenario

High-Resolution Experiments for Mixing in Large Enclosures

“…4097). Based on the LDV measurement, a fully developed velocity profile has been reached for both Reynolds numbers before entering the dome (Mao et al, 2023a). The values of turbulent intensity at the center of the pipe, according to the measurement from LDV, are 7.8%(𝑅𝑒 = 6021) and 8.7%(𝑅𝑒 = 4097), respectively.…”

“…The results from the convergence plot are not shown in this work for brevity and the reader is referred to Mao et al (2022) for the detailed evaluation method. The uncertainty quantification also follows the same procedure mentioned in Mao et al (2022Mao et al ( , 2023a. The uncertainty of the flow rate was estimated to ±2.7 × 10 −5 kg∕s based on the specification of the flow controller.…”

“…The distribution of jet half-width 𝛿 1∕2 , which is defined as the location where the mean streamwise velocity is equal to half the local jet maximum mean velocity, can be inferred from the distance between the two yellow lines. Jet half-width is often used to characterize the spreading rate of the jet (Mao et al, 2023a;Khayrullina et al, 2017;Pope, 2001). For the turbulent free-round jets, the jet half-width was found to grow linearly as the distance from the inlet nozzle increased (Pope, 2001).…”

“…The combination of several phenomena, e.g., jet interaction and impingement, re-circulation, buoyant flows, and thermal stratification severely complicates the jet mixing behavior inside the large enclosure and also challenges the existing system-level codes and Computational Fluid Dynamics (CFD) models. The ability of system-level and CFD codes to model flow mixing in large enclosures accurately is still under active investigation (Hu, 2019;Manera et al, 2022 (Merzari et al, 2023;Manera et al, 2023Manera et al, , 2022 seeks to support the further validation and development of CFD models to enhance prediction of nuclear reactor designs during operational and accident scenarios in which mixing in large enclosure (Mao et al, 2023a;Leite et al, 2023;Iskhakov et al, 2023) and stratified fronts play an essential role (Mao et al, 2023c;Tai et al, 2023a,b). A 1/12th scale Michigan Multi-jet Gas-mixture Dome (MiGaDome) facility based on the Modular High-Temperature Gas Reactor (MHTGR) upper plenum has been designed and constructed to quantify flow mixing in large enclosures under this project.…”

“…This hierarchical approach aims to ensure model robustness by relying on unit physics and sub-system level validation exercises. A previous study has investigated the flow mixing in the MiGaMome facility under an isothermal condition with single-jet and triple-jet injections (Mao et al, 2023a). The experimental data has been used for the validation of the state-of-the-art GPUoriented CFD code NekRs.…”