Establishment And Application Of Multiphase Flow Model In Square Arc Angle Aquaculture Tank

The aquaculture industry is undergoing a substantial transformation from traditional extensive mode to intensive mode in modern times.As a new and efficient aquaculture mode,Recirculating Aquaculture System could be used to reasonably design and optimize the structure of aquaculture tank,which plays a crucial role in loosening the restriction of limited resources and the demand of efficient output.In the Recirculating Aquaculture System,the research on the flow pattern of the aquaculture tank system at home and abroad is still in its infancy,and the relevant research on the systematic analysis of the impact of the inflow structure on the internal flow field characteristics of the aquaculture tank is not in-depth.The effects of jet angle and relative inflow distance on the flow field characteristics and particulate emission characteristics in single-channel aquaculture tanks were studied in this paper,where the hydrodynamic characteristics and particulate emission characteristic of the aquaculture tanks with different inflow structures were analyzed as well in hope to provide certain theoretical basis for influent structure design of the Recirculating Aquaculture System.For the purpose of studying the effect of influent system optimization on flow field characteristics of square-arc-angle aquaculture tank,computational fluid dynamics simulation(CFD)and RNG k-ε turbulence model were adopted here to build a 3D numerical turbulent liquid phase model and a DPM multiphase flow numerical model for square-arc-angle aquaculture tank.Numerical simulations of hydrodynamic characteristics of the square-arc-angle aquaculture tank with straight double tubes and arc-wall single tubes were carried out based on the verification of model precision.Based on the results of multiple working conditions,the optimal inflow structural parameters of the aquaculture tank are determined to optimize the hydrodynamic conditions in the aquaculture tank,and the influence of the optimization of inflow structure conditions in the aquaculture tank system on the performance of sewage discharge characteristics is analyzed.The main research contents and results are as follows:1.Four typical aggregation forms of settled solid particles during particle discharge process in the aquaculture tank were proposed to standardize the evaluation of particle aggregation states during particle discharge process in aquaculture tank system.2.Turbulent numerical model of the square-arc-angle aquaculture tank constructed was established using CFD technology,and the hydrodynamic characteristics of aquaculture tank from different jet angles under straight double tube inflow were discussed in hope to provide theoretical basis for influent structure design of recirculating aquaculture tank.If the jet angle of the straight double tube aquaculture tank is in 0°～10° under the same number of cycles,when,water velocity is higher and flow field is more uniform.The effect is optimal when jet angle reaches 0°.3.The influence of different C/B ratios(parameter C/B refers to the ratio of horizontal distance C from the center of jet tube to the wall of the aquaculture tank to length B of the short side of the tank)and different jet angles of arc-wall single tube aquaculture tanks on the flow field characteristics in the aquaculture tank system were studied.As revealed by the results,when C/B=0.07-0.09 and jet angle is 25°,the flow state of aquaculture tank is generally superior to that under other conditions.4.The numerical calculation model of solid-liquid multiphase flow was constructed here.Based on the liquid model of single-channel single tube arc-wall aquaculture tank,the influent structure conditions were optimized,and the influence of distribution rules of settled solid particles and discharge rate was analyzed to provide certain theoretical basis to improve sewage collection and discharge performance of aquaculture tank system.Physical model sewage discharge experiment was carried out as well to verify the accuracy and scientificity of solid-liquid multiphase flow model.5.The variation rule of optimal jet angle of inflow structure of the single tube arc-wall aquaculture tank with different C/B ratios was proposed,and the optimal combination of relative inflow distance and jet angle was analyzed in depth with a view to providing appropriate inflow conditions for improving the flow field environment and sewage collection and discharge performance of the aquaculture tank system.