基于CFD的养殖水体固液旋流分离装置数值模拟与验证

为探究旋流分离装置对水产养殖水体的分离效果,采用计算流体力学方法对旋流分离装置内部的流动特性进行数值模拟,得到了不同入口流量、不同入口浓度对固液分离性能的影响,通过试验数据对模拟结果进行了验证。模拟结果表明:随着入口流量的增加,分离装置内部流体速度增大,湍流流动增强,不利于固体颗粒的沉降。当入口浓度增加时,筒内流体运动速度降低,滞留在筒体中的颗粒浓度增加,降低了固液分离效率。入口流量和入口浓度的增加均会导致不同粒度颗粒分离效率下降,且随着颗粒粒度的增大,分离效率下降幅度增大。通过与试验数据相比,模拟误差在10%以内,模拟结果可信。该研究可为旋流分离装置在水产养殖领域的应用提供参考。

Numerical simulation and validation of solid-liquid cyclone separation device for aquaculture water based on CFD

With the continuous improvement of the scale of breeding, the deterioration of water resources and environmental pollution, the breeding model needs to be transformed into an efficient and sustainable direction. The industrial farming system has the advantages of short culturing period and high yield per unit area. However, due to the large amount of solid wastes generated with high density of industrial farming, the removal of large particles of suspended solids in water is the primary task of waste treatment. As a centrifugal separation device, the cyclone separator has been widely used in petrochemical, sewage treatment and other industries. In order to explore the separation effect of solid-liquid cyclone separation device on aquaculture water, the computational fluid dynamics (CFD) method was used to simulate the flow characteristics of the cyclone separation device. At first, hybrid meshing of the cyclone separation device model was finished using the pre-processing software Gambit 2.4.6. In order to improve the accuracy of simulation, the mesh of inlet, overflow port and bottom flow port were all encrypted. The grid independent validation was done to choose the acceptable mesh. The inlet of the cyclone device was set as the velocity inlet, and the bottom flow port and the overflow port were set as pressure outlets. At last, the mesh was imported in Fluent software to analyze the effects of different inlet flow rates and different inlet concentrations on solid-liquid separation performance. In this simulation, the coupling of velocity field and pressure field was achieved by a semi-implicit method in the pressure correction method. First-order upwind difference scheme of convection motion was selected for the interpolation method of the diffusion term, the source term and the convection term. And the wall surface region was treated by the standard wall function. In order to compare the flow field distribution characteristics under different parameters, X=0 of the longitudinal section at 1/2 of the overflow pipe was set as the flow field monitoring surface, furthermore, 1/4 of the cone section and 2/3 of the column section on the monitoring surface were taken as the flow field monitoring lines. The simulation results show that as the inlet flow rate increases, the low-speed area in the middle of the cylinder reduces, and the area of the outer swirling area increases. Moreover, fluid velocity inside the separation device increases, and the turbulent flow increases, which is detrimental to the sedimentation of solid particles. Increasing the inlet concentration will increase the amount of particles in the cylinder and the interaction between particles is enhanced. In addition, the fluid velocity in the cylinder decreases, and the concentration of particles retained in the cylinder increases, which reduce the solid-liquid separation efficiency. The increase of the inlet flow and the inlet concentration leads to a decrease in separation efficiency of particles with different particle sizes. And the larger the particle size, the more significant the separation efficiency decreases. According to the comparison between simulation results and experimental data, the simulation error is less than 10%, and the simulation results are trustworthy. This study can provide a reference for the application of cyclone separation devices in aquaculture.