A computational fluid dynamics study on the optimisation of a circular sedimentation tank using perforated inlet baffles

Abstract

A numerical study on a circular sedimentation tank is done to investigate the effect of perforated inlet baffles on the efficiency and performance of the sedimentation tank. A total of three new modified geometries with perforated baffles placed at strategic locations in the inlet region were studied and compared with the original sedimentation tank that contains an ordinary stilling well and a McKinney baffle. The Euler-Lagrange approach of multiphase modelling is employed in this study using the Discrete Phase Model. The numerical model employed in this study was validated using experimental data from the literature. It was observed that the perforated baffles are effective in dissipating the kinetic energy in the inlet region and also helps in producing a more distributed and tranquil flow in the settling region. Of the four cases studied, case-4 is found to be the most efficient with 58.36% total settling efficiency, which is an increase of 10.96% from that of the original tank. However, it was also found that case-3 can also be considered a viable option for the retrofitting project if a slight compromise in performance enhancement could be tolerated in exchange for a more efficient utilisation of the added materials. Comparisons of the different cases studied have also been conducted through quantitative and qualitative assessments, employing calculated settling efficiencies and the analysis of velocity magnitude contours, turbulence kinetic energy contours, and particle trajectories obtained through the numerical simulations.