Numerical simulation of thermal convection over anfd through an internally heat porous medium

Hamtiaux, Victoria [UCL] Papalexandris, Miltiadis [UCL]

In this work, we perform numerical simulations of natural thermal convection in a cuboidal domain that includes an internally heated porous region. 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 Spent Fuel Pools (SFP). In this respect, the fuel racks can be modeled as a porous medium immersed in water. Typically, in previous studies of such flows, the interstitial fluid and the solid matrix of the porous medium are assumed to be in thermal equilibrium. However, in many applications, including SFP, the validity of this assumption becomes questionable; for this reason, it is not invoked herein. The mathematical model that we employ for our simulations is based on the single-domain approach. According to it, the porosity is introduced as a field variable, thereby allowing the formulation of a single set of governing equations valid in both regions. Our study consists of direct numerical simulation of turbulent thermal convection in a domain that contains an internally heated porous region right off the bottom wall. The resulting turbulent convection in the pure-fluid region, above the porous medium, corresponds to a number of Ra = 8.6 x 10^5. Herein, we provide a description of the flow structures and the temperature distribution for the two phases. Further, we present and discuss results for the turbulence statistics in the pure-fluid region.