Study On Flow Characteristics Of Aquaculture Ponds

With the shortage of water resources and environmental pollution becoming increasingly prominent,industrial circulating aquaculture system(Recirculating aquaculture systems)as an intensive aquaculture model has also been widely promoted.Some scholars predict that by 2030,the RAS aquaculture model will become the main source of aquatic products,as it meets many environmental,economic and social sustainable development goals.As the core of RAS system,aquaculture ponds provide essential elements such as water sources and nutrients for aquatic organisms.How to design an aquaculture pond that is most suitable for the growth of aquaculture objects has become an urgent problem to be solved.One of the key factors to guide the design of the structural parameters and operation parameters of the aquaculture pond is to know the motion state in the aquaculture pond accurately.Therefore,it is necessary to simulate the whole flow state of the aquaculture pond under the action of circulating water,analyze the flow field and study the hydrodynamic characteristics.This paper makes an in-depth study and summary of the turbulence simulation of the culture pond,uses the CFD theory method to identify and select the turbulence model which is more in line with the actual situation,realizes the simulation of the internal flow field of the culture pond,and relatively comprehensively describes the physical quantities such as the water velocity of the internal flow,the trajectory of solid particles and the residence time of the target culture pond under the dynamic action of circulating water.A design standard evaluation of structural parameters based on the change of flow field in aquaculture pond is realized.The main research contents are as follows:First,understand the basic theory and research methods of turbulence simulation in aquaculture ponds at home and abroad,and further master the theoretical process of finite volume method and finite difference method for solving three-dimensional N-S equations and turbulence model equations.The pressure implicit solution method,the first-order upwind discrete scheme of turbulent flow energy,and the SIMPLE algorithm of pressure-velocity coupling are studied.Based on the above numerical simulation methods,the inherent mechanism of turbulence simulation was studied.On this basis,through the CFD commercial software FLUENT,the 3D model creation and numerical simulation of the target aquaculture pond are completed.Among them,the RNG model and the standard model were used to simulate the water flow in the pond,and a turbulence model that was in good agreement with previous test results was obtained.The results were compared with the test results to verify the accuracy of this method.Based on the above,a further study of the two-phase flow in the target breeding pond was conducted,and the trajectory and running time of solid particles of different diameters in the pond were obtained.Through numerical simulation of the aquaculture pond,the influence of the structural parameters and operating parameters(such as the number of water inlets,the direction of the water inlets and the water speed)on the distribution and changes of the internal flow field of the aquaculture water And make regular explorations in order to provide constructive guidance for the design of aquaculture ponds.