| Artificial upwelling technology is a new technology.It can elevate the deep seawater rich in nutrients to the ocean surface,improve the primary productivity of ocean surface,increase carbon sink and improve the marine environment.In order to provide a valuable reference for the optimization of air-lift artificial upwelling system,this paper mainly focuses on the numerical simulation of the artificial upwelling.Based on the research of artificial upwelling,the main research tasks are as follows;First,study the type of gas injection nozzle.Second,study the number of holes in gas injection nozzle.Third,study the depth of gas injection.Fourth,study the rising pipe type.Fifth,preliminary study of deep water in the diffusion of water in the range.For the above research tasks,CFD numerical simulation method is mainly used to study,the work flow is as follows.First,according to the Qiandao Lake test to establish a full-scale model of the surge tube geometry and computational domain geometry model.Second,the VOF method is used to simulate the artificial upwelling in the commercial software STAR-CCM+.The simulation is mainly to monitor the ascending flow of the deep water.Thirdly,the calculation results are verified.The first step is to verify the independence of the grid The second step is to conduct the data validation.Fourthly,the CFD numerical model are used to calculate the water lifting flow rate of different water injection nozzle types,different injection holes,different gas injection depths and different surge tubes.Fifthly,the research on the diffusion range of the deep water re-established the surge tube and the computational domain geometric model.VOF method is also used to calculate the diffusion range of deep water in the commercial software STAR-CCM+ at different discharge velocities and different tube types.Based on the above research objectives,tasks,workflow,etc.,this paper was completed.The following results have been gained.First,the annular gas injection nozzle than the cross injection nozzle,can be more to enhance deep water.Second,when the number of injection holes is 24,the flow rate of the deep water is larger than that of 384 holes.Third,with the increase of gas injection depth,the ascending flow rate of deep water increases.Fourth,when the top diameter of the top expansion tube is 0.6m and 0.8m,the depth of water body can be increased more than that of equal diameter(0.4m diameter)pipe.But when the top diameter is 1.0m,the lifted deep water flow rate is lower than that of equal diameter pipe.When the top diameter of the top shrink pipe is 0.3m,0.2m and 0.15m,the ascending depth of water flow is not as large as that of equal diameter pipe.Fifth,the jet speed increases,the range of deep water diffusion will also increase.In the case of the top shrink tube,the diffusion range is almost constant as the discharge velocity increases.Sixth,in the case of the same discharge rate,the largest diffusion range is the top expansion tube,followed by the same diameter tube,the smallest range is the top of the contraction tube.Analysis of the above results,the following conclusions have been gained.In the surge tube of the gas injection design,if from the vicinity of the pipe wall of the surge tube will be better than the injection of gas from the middle of the surge tube.The small injection holes is not conducive to enhance the deep water.The depth of gas injection is beneficial to enhance the deep water.But this will increase the difficulty of engineering.In the actual air-lift artificial upwelling system this design can be adjusted according to different on-site conditions.Enlarging the diameter of upwelling pipe appropriately can not only increase the deep water flow rate,but also be beneficial to deep water diffusion. |
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