Large eddy simulations of isothermal and non-isothermal turbulent flows for high temperature gas cooled reactors

In order to develop an experimentally validated computational model for the lower plenum of High Temperature Gas-Cooled Reactors (HTGR), three separate Large Eddy Simulation (LES) studies are conducted. First, detailed study is made of LES for an isothermal turbulent jet, which is compared to well-accepted experimental data. Inconsistencies in the literature surrounding the Reynolds number dependence for the turbulent statistics are comprehensively addressed. Second, a non-isothermal LES study of flow over a cylinder is conducted, and includes comparison between experimental data and LES for different subcritical Reynolds numbers. The final study is that of LES for a nonisothermal round jet, where the effect of a precursor simulation is found to play a vital role for capturing the underlying physics within the turbulent Navier Stokes and energy equations. Good agreement is obtained between our LES predictions and experimental measurements in both near-field and far-field data. This research lays the groundwork needed to develop high-fidelity, experimentally validated computational models of the complex mixing flow in the HTGR lower plenum.