A comparative assessment of different experiments on buoyancy driven mixing processes by means of CFD

•Systematic model assessment on basis of similar experiments in different facilities.•Focus on highly transient and 3D buoyancy driven mixing processes.•U-RANS approach is capable to capture the phenomenology.•Impact of initial and boundary conditions on the predicted mixing process identified.•Experiments need quantification of wall heat transfer and flow pattern.

Containment flows are driven by density differences in the long term of an accident scenario. A systematic CFD validation has been performed and is presented in terms of a comparative evaluation of two different tests in the German THAI and French MISTRA facilities. The simulation results demonstrate the general capability of CFD to predict such flows but also reveal a significant sensitivity to the defined initial and boundary conditions.