Numerical simulation of secondary sedimentation tanks using the VOF method for modeling the free surface

Secondary sedimentation tanks are one of the most important parts of water treatment plants. In these tanks, settling of suspended particles occurs by means of gravity. In the present study, flow in a rectangular secondary sedimentation tank has been investigated numerically using the VOF method for modeling the free surface and also the RNG model. In the presented model, in addition to the analysis of the free surface, the effect of the particleparticle interaction and buoyancy forces is also considered. Numerical simulations have been done using the open source software OpenFOAM. In order to model the particles in the flow, the relevant code has been expanded. By comparing the concentration values in the presence of particles with those from the experimental results, the importance of particle size distribution and changes in the particle size relative to the mean particle diameter can be observed. Furthermore, the results indicate that the performance of sedimentation tank is closely related to the size of the particles