Numerical simulations of turbulent thermal convection in mixed pure fluid – porous domains.*

In this talk we report on numerical studies of turbulent thermal convection in domains with immersed porous structures that are heated internally. The main motivation for this study comes from the need to better understand the phenomena occurring in the early stages of a loss of cooling accident in storage pools of spent nuclear fuel. In this respect, the fuel racks that radiate heat are macroscopically modeled as a porous medium, with water being the working medium. In the first part of this talk we briefly present the mathematical model, which is based on the single-domain approach. In the second part, we discuss and analyze the results of Direct Numerical Simulations of turbulent convection in a cubical cavity that includes a porous region located at the bottom of the domain and away from the side walls. The porosity of this region is equal to 0.6. The Rayleigh numbers considered herein are in the range 10⁶ < Ra <10⁸, which corresponds to moderate turbulent intensities. Besides the analysis of turbulent statistics, we elaborate on the convective patterns and turbulent structures inside the porous medium as well as on the effects of the secondary flows adjacent to the porous region.