Simulation of a Two-Phase Fluid Flow in a Design Solution of a Secondary Radial Settling Tank for Wastewater Treatment

This report examined a design solution for a wastewater treatment facility in which—based on input data such as the amount of suspension at the inlet—the solid content in the suspension and sludge, the relative weight of the particles, the sedimentation rate, the diameter and height of the radial settler were determined. After determining the parameters, the design solution was created in the SolidWorks 2024 environment. In the design process, the shape of the fastening device was modified, which is of significant importance in the design of the facility, as it affects in a specific way the concentration of suspended substances in the thickened sludge and in the recirculated sludge flow. The design was transferred into the ANSYS CFX 2017 software for subsequent simulation of its purification function. Based on techniques in fluid mechanics, the boundary and end conditions for the analysis of the fluid flow were set. The study focused on the analysis of a CFD model to describe the movement of a two-phase fluid consisting of rainwater and sand with a particle size of 1–10 mm. Based on the analysis, the results of the influence of rotating elements on the movement of the solid phase and water in the fluid domain were reported.