Jet–Crossflow Interaction in HTGR-Relevant Configurations: Effects of Velocity Ratio and Jet Spacing Using RANS and URANS

This study looks at how three round jets interact with a turbulent crossflow, similar to coolant flow in the lower plenum of a high-temperature gas-cooled reactor (HTGR). We first simulate a single jet in crossflow as a baseline to check basic flow features, then extend to steady RANS simulations of three jets to see how changing the jet-to-crossflow velocity ratio (VR = 0.5–1.6) and jet spacing (S/D = 3–7) affects mean jet penetration and flow mixing. To check what steady RANS misses, we also run one URANS simulation for a selected case to show unsteady flow structures that steady models cannot capture. The CFD results are compared with experimental data for validation of mean flow trends. The goal is to understand how these basic flow parameters control mixing and recirculation zones in a multi-jet crossflow, and to show where unsteady modeling is needed for more accurate predictions.