Numerical modelling of fluid flows in a recirculating aquaculture system

迈埃拉集团开发了一种新的、创新的循环水产养殖系统(RAS)，希望成为偏远地区食品安全解决方案的领导者。RAS基于模块化的水箱设计，在养鱼过程中提供有针对性的喂养、用药和环境控制。这一新颖的设计采用气升式泵送机构来控制水速，通过运动来优化鱼类的健康，同时促进气体交换和废物的清除。气升式泵内的流体流动是非常复杂的两相(气液)泡状流和质量交换的组合。相互作用以改变流体速度和空气交换的参数是空气的质量流量、气泡大小、气举管道几何形状以及到模块化储罐的管道连接。预测这些参数的变化对系统性能的影响是非常具有挑战性的，但对于改进系统的设计是必不可少的。本文的主要工作是建立RAS气升泵内三维两相流体流动的详细数值模型。该模型将使用最先进的计算流体力学(CFD)软件，并与实验数据进行验证。所得到的模型将预测流体的流动和传质，并对几何和操作条件的变化做出响应。该公司将能够使用该模型进行设计变更的虚拟原型制作。这将节省时间和金钱，朝着全面生产所需的改进设计迈进。

A new, innovative, recirculating aquaculture system (RAS) has been developed by the Myera Group that wants to be a leader in food security solutions for remote regions. The RAS is based on a modular tank design that provides for targeted feeding, medication, and environmental control in the raising of fish stocks. The novel design uses an airlift pumping mechanism to control water velocity for optimising fish health through exercise, while simultaneously promoting gas exchange and removal of waste.The fluid flow in the airlift pump involves a very complicated combination of two-phase (gas-liquid) bubbly flow with mass exchange. The parameters that interact to change the fluid velocity and air exchange are the mass flow rate of air, the bubble size, the air lift duct geometry, and the piping connections to the modular tank. Predicting how changing any of these parameters will affect the performance of the system is very challenging, yet is essential to improve the design of the system.The main aspect of this proposed work is to develop a detailed numerical model of the three-dimensional two-phase fluid flow in the airlift pump of the RAS. This model will use state-of-the-art computational fluid dynamics (CFD) software and validate against experimental data. The resulting model will predict the fluid flow and mass transfer and be responsive to changes in the geometry and operating conditions. The company will be able to use the model for virtual prototyping of design changes. This will save time and money in moving toward improved designs that are needed for full scale production.