Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

1 Publication

Experimental studies and CFD calculations for buoyancy driven mixing phenomena

Da Silva, M. J.; Thiele, S.; Höhne, T.; Vaibar, R.; Hampel, U.

In nuclear reactor safety the mixing of borated and deborated water is a critical issue that needs investigation, assessment and prediction. Such mixing is buoyancy driven and numerical codes must correctly model momentum transfer between components of different density. To assess and develop CFD models for buoyancy driven mixing we set up a simple vertical mixing test facility (VeMix) and equipped it with a newly developed planar electrical imaging sensor. This imaging sensor acquires conductivity images of the liquid at the rear channel wall with a speed of 2,500 frames per second. By adding NaCl tracer to the denser component we were able to visualize the mixing process in high spatial and temporal detail. Furthermore, an image processing algorithm based on the optical flow concept was implemented and tested which allows the measurement of flow pattern velocities. Selected experiments at different Richardson numbers were run with two components of different density (pure water and glucose-water mixture) simulating borated and deborated water in a light water reactor scenario. These experiments were compared to CFD calculations using standard turbulence models. Good agreement between experimental data and first CFD simulations was found.

Keywords: buoyancy driven flow; mixing; deborated water; flow visualization; CFD; simulation; planar array sensor

  • Nuclear Engineering and Design 240(2010)9, 2185-2193