Experimental studies and CFD calculations for buoyancy driven mixing phenomena

Buoyancy driven flow is found in many engineering application such as the mixing of fluids with different densities. In nuclear reactor safety the mixing of borated and deborated water is a critical issue that needs investigation, assessment and prediction. Recent progress in computer hardware and numerical techniques has made it viable to predict these mixing patterns using CFD codes. However, as CFD codes contain more or less empirical models it is necessary to validate the predicted results using experimental data. Therefore, a combined numerical and experimental study of buoyant mixing processes has been performed. A newly developed planar sensor was applied to experimentally investigate the mixing process. Validation experiments were performed in the VeMix test facility, which show typical vertical and horizontal flow pattern under different flow regimes. The data from the planar sensor of mixing behavior and velocity fields were used for the validation of the simulation results. Comparisons of the experimental results with the corresponding simulations show similar flow patterns and typical periodic behavior.