The Three-dimensional Numerical Simulation Study Of Radial Flow Sedimentation Tank Based On CFD

As one of the sewage treatment plant, Out-feed Peripheral-overflow Settling Tank is widely used in a precipitation structures. Due to the complexity of tank size and structure, in the process of actual operation, the design parameters of sedimentation tank and the surrounding environmental factors will affect the precipitation effect. However, at present, the parameter selection of some of the design is broad, which will greatly influence on precipitation effect, so the study of Out-feed Peripheral-overflow Settling Tank is very necessary.Based on CFD method, and mathematical model of two phase flow was used for the study of numerical simulation. By changing the location of center into the well water hole, the shape of water hole, bottom slope and the size of inflow suspended particle etc, we simulated the operation situation under different working conditions, and analyzed flow field, concentration field and settling basin. The results were showed:(1) The location of central inlet well hole has a great effect on the removal rate of suspended matter for radial sedimentation basin. When a single pool of processing capacity of 1225 m3/h radial flow sedimentation tank model simulation, as the location of hole increased from 0.1 m to 0.3 m, the tank volume utilization ratio and the suspended matter removal rate will be improved. While the location of hole increased from 0.3 m to 0.9 m, both the tank volume utilization ratio and the suspended matter removal rate will be reduced to poor sedimentation efficiency. When a single pool of processing capacity of 291.7 m3/h radial flow sedimentation tank model simulation, the best location of hole was 0.2m. Comprehensive two model simulation results show that the hole location in the center of the well into the 1/24-1/7, the removal of suspended solids higher settler better.(2) The hydraulic radius of hole is gradually increased when the shape of hole various from circular to square then changes to hexagon, so the turbulence intensity of liquid in the tank is reduced. Therefore, it’s good for the sedimentation of suspended particle, and better sedimentation efficiency.(3) The bottom slope of Out-feed Peripheral-overflow Settling Tank had great influence on precipitation in the settling tank:when the bottom slope increased from 0 to 0.05, the removal rate of suspended matter increased, and the effect of precipitation has better performance; But when the bottom slope increased from 0.05 to 0.09, the removal rate of suspended solids has slightly decreasing. The most suitable for bottom slope was 0.05.