Numerical analysis of flow and settling efficiency in a sedimentation basin

Abstract This paper has assessed the flow patterns and settling efficiency in the sedimentation basin using the particle tracking method of the CFD code and has reached the following conclusions: In the original design where no baffle is installed in the sedimentation basin, a large recirculating area where the flow stagnates is created in the right side of the sedimentation basin, with most of the particles moving to the left side of the sedimentation basin following the flow. This biased flow structure in the sedimentation basin reduces the residence time of particles and thereby undermines settling efficiency. The biased flow toward the left side of the sedimentation basin is alleviated by installing a baffle in the sedimentation basin, promptly reducing the fast flow of over 0.7 m/s in the inlet of the sedimentation basin to the rate below 0.2 m/s. In this paper’s simulation conditions, if a one-sided baffle is to be installed in the sedimentation basin, placing it 15 meters away from the basin’s inlet leads to the best settling efficiency; it has also been analyzed that installing a two-sided baffle—rather than a one-sided one—is a better option in terms of settling efficiency. The highest settling efficiency of 96.2% is achieved when the underwater length of the two-sided baffle is set at 8 meters.Key words : settling efficiency, sedimentation basin, particle tracking method, one-sided baffle, two-sided baffle주제어 : 침사효율, 침사지, 입자추적기법, 일방향 baffle, 양방향 baffle