CFD Study of Effect of Particles on Flow Patterns and Separation in Settling Tank

In the present work, the effects of particles on the flow patterns in settling tanks are studied with a computational fluid dynamics (CFD) model with various nondrag forces. The CFD model is validated with radial velocity measured with ultrasonic velocity profiler and concentration profiles for a lab-scale settling tank and industrial settling tank. The effects of lift, turbulent dispersion, and particle-fluid interaction forces are investigated on the flow patterns. The effects of particle characteristics are also studied on the separation. It was observed that instead of monodispersed particles, particle size distribution should be incorporated in the CFD model for better prediction of the concentration profiles. The forces acting on the particle shift the recirculation pattern in the settling tank. Different particles with the same Archimedes number exhibited different flow patterns. Similar flow patterns and separation efficiency is predicted for different particles with similar terminal settling velocity.