Numerical analysis of natural convection behavior in density stratification induced by external cooling of a containment vessel

It is essential to improve computational fluid dynamics (CFD) analysis accuracy to estimate thermal flow in a containment vessel during a severe accident. Previous studies pointed out the importance of the initial and boundary conditions on the analysis. The purpose of this study is to evaluate the influence of initial and boundary conditions by numerical analysis of natural convection experiments. A density stratification layer was initially formed, and natural convection was induced by the external cooling of the vessel. Mixing by natural convection eroded the density stratification. We applied the RANS model with dynamic turbulent Schmidt number model. We used the measured temperature and gas concentration as the boundary and initial conditions. The erosion velocity did not change much with the initial gas distribution. The temperature boundary condition of small internal structures significantly influenced the fluid temperature distribution, and we evaluated this influence of the small internal structure quantitatively.
source:https://www.sciencedirect.com/science/article/pii/S0306454921007441?via%3Dihub