Numerical simulation of multicomponent flows with the presence of density gradients for the upgrading of advanced turbulence models

Highlights: • Turbulence effects during the buoyancy-driven mixing were investigated. • Additional buoyancy terms were included in buoyancy-modified turbulence models. • Vortical oscillations showed good agreement between simulations and experiment. - Abstract: The turbulence effects during the buoyancy-driven mixing was investigated at a vertical mixing (VeMix) test facility, which was developed to investigate the mixing of high borated and low borated coolant in nuclear reactor. Additional buoyancy terms are included in buoyancy-modified turbulence models, which have been implemented in the CFD code ANSYS CFX and validated with experimental data captured by optical methods and conductivity measurement technology. The physicality of the flow phenomena and the vortical oscillations analyzed by Fourier transformation in both the experiments and simulations show good agreement under different flow conditions. The influence of different buoyancy models were investigated in detail and optimal models for simulations at similar flow conditions have been selected.