Buoyancy driven flow in the VeMix test facility

Buoyancy driven flow is often presented in many engineering application such as mixing process of fluids with different density. The aim of our study is to simulate mixing processes that are relevant in safety analyses of nuclear reactors. The boron dilution problem is one such safety issue analysis.
Borated and unborated water are of different densities and may be of the diffenrent temperatures, what causes additional density defferences. The degree of mixing of low and high borated coolant is a critical issue with respect to reactivity insertion into the reactor core. As nuclear reactor geometries are complex, the mixing process not widely understood and the influence of the buoyancy is small, a very simple vertical test facility was chosen for validation of numerical models of the mixing process. A new source term, which consists of a sum of the component turbulent density fluxes, is defined for the turbulent model and in this case is based on the definition turbulent kinetic energy.