CFD simulations of thermal stratification in a large enclosure

Thermal stratification develops in a wide range of thermal systems when fluid(s) of two or more densities, stemming from different temperatures, interact. Data are presented where a single vertical narrow rectangular hot water jet of Reynolds number ranging from 8000 to 12000 enters a large tank and the hot fluid stratifies in the tank. Temperature data are collected using thermocouples submerged at varying depths in the water, and visual data from dye in the hot jet was collected for selected runs. A 3-D volume model of the experiment from Autodesk Inventor is the starting point for a CFD model developed using Altair HyperWorks product suite. The simulation of thermal stratification within the tank was developed using Altair AcuSolve, a CFD solver based on finite element analysis. The results from the CFD model are presented and compared against the temperature data. The CFD predictions for the jet and plume flow are also compared with a legacy model based on similarity solutions. These comparisons provide a limited validation of the simulations from AcuSolve. While overall agreement between experiment and simulations is good, the detailed comparison of CFD results with data presented in this paper indicate mixing physics models need improvement in the free shear flow of the jet, and diffusivity models need improvement in the tank volume away from the jet.