Simulation von Vermischungsvorgängen

Buoyancy driven mixing was investigated under simulated natural circulation conditions at the test facility ROCOM.
Experiments with density differences between the ECC water (higher density) resp. the de-borated slugs (lower density) and the ambient coolant was used to validate the CFD software CFX.
A Reynolds stress turbulence model was employed to model the effects of turbulence on the mean flow.
Hybrid meshes consisting at least of 2 million nodes and 4 million elements were used.
The experiment and CFD calculations show in both cases significant mixing effects due to the density differences.
The ANSYS CFX calculations show a good qualitative agreement with the data. At some local positions differences in the predicted and measured concentration fields occur.