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Two- and three-dimensional simulations of Rayleigh–Taylor instabilities using a coupled Cahn–Hilliard/Navier–Stokes model

par Anne-Marie - publié le

During a severe nuclear accident, due to the loss of cooling, the reactor core can melt. This results in the build up of a liquid mixture made of uranium and the metallic component of the reactor (mostly steel and zirconium). This liquid mixture is heating continuously due to uraniun radioactivity. In order to improve the safety of nuclear reactors in the case of such an accident, a good understanding of the thermal exchange in Corium is necessary. And among the physical mechanism that govern the thermal exchanges, the multiphase flow that takes place between the steel rich phase and the uranium rich phase that are present in Corium is believed to play an important role. As a first step toward a quantitative modeling of these phenomena of fluid flow coupled to chemical species diffusion we have studied, in collaboration with a team from CEA, the Raileigh Taylor instability using a Cahn Hilliard model coupled to the Navier stokes equation of fluid flow.

The results, presented in an article published in Physics of Fluids show that the model can reproduce theoreticaal predictions with a very good accuracy. They also give some light on the convergence of diffsue interface models in the study of multiphase flows.