Application of Stress Blended Eddy Simulation to the prediction of clarified layer depth and solids suspension in a draft tube reactor

Predictions of clarified layer depth and solids suspension in a draft tube reactor were investigated at a moderate solids loading of 16% v/v using both a RANS approach (k−ε) and a scale-resolving approach using Stress Blended Eddy Simulation (SBES). The multiphase flow was modelled using an Algebraic Slip model and the impact of drag law, turbulent particle diffusion and number of particle size classes was examined. The inclusion or exclusion of turbulent particle diffusion is found to dominate the RANS results, with resulting poor prediction of clarified layer depth and solids suspension under some conditions. In contrast, the SBES model is found to give good agreement with experimental data and the results show there is no need for a modelled turbulent dispersion force in this system if the large-scale turbulence structures responsible for particle transport are explicitly resolved.