Numerical Simulation And Optimization Improvement Of V-type Filter Based On CFD Technology

In this paper,CFD technology is used to simulate three different working conditions of the common V-type filter,including water intake distribution,filtration and water distribution of backwashing.The flow patterns in the structures under various working conditions are analyzed based on the simulation results,and the methods to improve the uniformity of the intake water distribution and backwash water distribution of V-type filters are proposed,which can provide reference for the design of V-type filters in practical projects.The fluid volume model(VOF)and turbulence model in Ansys Fluent were used to simulate the fluid with free surface in the intake distribution channel of V-type filter by computational fluid dynamics(CFD).By adjusting the position of the intake pipe,the weir height and the weir width of the distribution channel,the uniformity o f water distribution is optimized.The simulation results show that adjusting the position of the intake pipe has little effect on improving the uniformity of water distribution;adjusting the weir height and width can increase the uniformity of water distribution channel by more than 10%.It is also found that adjusting weir height is more sensitive to the change of water distribution uniformity,which is also the reason why weir plate is usually set in V-type filter in actual construction,and weir height can be adjusted by adjusting weir plate during trial operation.The porous medium model and turbulence model in Ansys Fluent were used to simulate the filtration conditions of V-type filter with clean homogeneous media.The simulation results show that the distribution of water flow in the upper space of the sand surface is not uniform when V-type filter is used.Breadthwise,the velocity at one end of the V-shaped groove is higher than that at the other end of the drainage groove;lengthways,the velocity at the front and back ends of the V-shaped groove is higher,while the velocity at the middle section of the V-shaped groove is smaller.This non-uniformity is caused by the unreasonable way of intake of V-shaped groove.Although this will affect the flow distribution in the filter layer,the simulation results show that the flow velocity range in the filter layer is 0.0046-0.0047m/s,which can be neglected.The turbulence model in Fluent was used to simulate the water distribution o f V-type filter backwashing with separate water.The simulation studies only the middle and bottom water distribution space.The simulation results show that the water distribution in the middle and bottom of the ordinary V-type filter is not uniform.The water distribution in the middle along the direction of water distribution is smaller,and the water distribution at both ends is larger.Through the analysis,it is found that the basic reason for the non-uniformity is that the hydrostatic pressure distribution in the distribution space is not uniform because of the different degree of recirculation of water flow at the front end of the distribution space.Based on the analysis of the simulation results,the measures to improve the uniformity of water distribution are proposed for the middle water distribution and the bottom water distribution respectively.For water distribution in the middle,the method of changing the size of the square hole is adopted;for water distribution in the bottom,a horizontal steel plate with different hole diameters is added in the space.The simulation results show that both methods can improve the water distribution uniformity of backwashing of V-type filter to a certain extent.