CFD modelling of a negatively buoyant purge flow in the body of a reactor coolant circulator

The paper describes a finite element flow calculation using a two-equation turbulence model and variable properties, which analyses the effect of injecting a negatively buoyant flow stream into the primary circuit of a gas cooled reactor. This flow is intended to purge moisture-laden gas from the compartment housing the electrical motors driving the primary circuit pumps. The study highlights the sensitivity to the use or otherwise of the Boussinesq approximation and the type of boundary conditions specified at the outlet of the calculational domain. The method of calculation was benchmarked against a challenging experiment on the mixing of stably stratified saline streams, as well as the higher order CFD modelling of the same experiment.