气力人工上升流的数值模拟研究

发布时间：2018-07-05 10:22

本文选题：气力人工上升流 + CFD数值模拟　；参考：《浙江大学》2017年硕士论文

【摘要】：人工上升流技术是借鉴自然上升流应运而生的开发利用海洋资源的新技术,它能将富有营养盐的深层海水提升到海洋表层,提高海洋表层的初级生产力,增加碳汇,改善海洋环境等。本文主要针对气力人工上升流技术进行数值模拟研究,研究不同参数对气力人工上升流提升流量的影响和深层水体的扩散范围。提升流量的增加和深层水体扩散范围的增大对提高海洋表面初级生产力,增加碳汇,改善海洋环境等具有重要的意义。在已有的气力人工上升流研究基础上,研究以下几个参数对于气力人工上升流提升流量的影响。一是研究注气喷头的类型,二是研究注气喷头的注气孔数,三是研究注气深度,四是研究涌升管管型。然后研究两个参数对深层水体扩散范围的影响,一是深层水体从管口喷出的速度,二是涌升管管型。针对以上研究任务,主要运用CFD数值模拟方法进行研究,工作流程如下。一是对课题组成员曾做过的千岛湖试验进行认真的学习分析,根据千岛湖试验的情况建立全尺度的涌升管几何模型和计算域几何模型,在商业软件STAR-CCM+中进行网格划分并运用VOF方法进行气力人工上升流的计算模拟。二是验证计算结果的正确、可靠性,第一步是网格独立性验证,分别用网格数为105万、121万、153万和189万四套网格计算不同注气量下的深层水体提升流量,最终选取网格数为153万的作为后续计算的网格;第二步是用CFD数值计算所得的深层水体流量去和试验数据作比较,试验数据和数值计算结果的趋势基本相符。三是利用验证后的CFD数值模型和网格分别计算不同注气喷头类型(十字注气喷头和圆环注气喷头),不同注气孔数(24孔和384孔)、不同注气深度(6.1m、9.6m、16.1m)、不同涌升管管型(顶部扩张管和顶部收缩管)情况下的深层水体提升流量。四是针对深层水体扩散范围的研究重新建立涌升管(等直径管、顶部扩张管、顶部收缩管)和计算域几何模型,在商业软件STAR-CCM+中进行网格划分并运用VOF方法计算深层水体的扩散范围。根据以上工作流程完成本文,得出如下结果。一是圆环注气喷头相较于十字注气喷头,能更多地提升深层水体。二是注气孔数为24孔时,提升的深层水体流量大于注气孔数为384孔时。三是随着注气深度的增加,深层水体的提升流量也增加。四是顶部扩张管的顶部直径为0.6m和0.8m时,与等直径(0.4m直径)管相比,能更多地提升深层水体,但是当顶部直径为1.0m时,其提升的深层水体流量反而低于等直径管;顶部收缩管(顶部直径分别为0.3m、0.2m、0.15m)提升的深层水体流量不如等直径管多。五是在等直径管和顶部扩张管情况下,喷出速度增大,扩散范围也随之增大。而在顶部收缩管情况下,随着喷出速度的增大,扩散范围基本不变。六是在相同喷出速度的情况下,扩散范围最大的是顶部扩张管,其次是等直径管,范围最小的是顶部收缩管。分析以上的结果,得出以下结论:在涌升管的注气设计中,如果从靠近涌升管管壁的地方注气效果会优于从涌升管中部注气;注气孔数的多少对应的是注气孔的大小,也就是气泡的大小,过小的气泡并不利于提升深层水体;注气深度大有利于提升深层水体,但是这会增加工程难度,在实际的气力人工上升流系统设计中可以根据不同的实地情况进行调整;适当地扩大注气喷头以上的涌升管管径不仅能增加深层水体的提升流量,对于深层水体的扩散也是很有益的。
[Abstract]:Artificial upflow technology is a new technology for exploiting and utilizing marine resources for reference to natural upwelling. It can raise the deep sea water of rich nutrients to the surface of the ocean, improve the primary productivity of the ocean surface, increase the carbon sink and improve the marine environment. This paper is a numerical simulation of the artificial upflow technology. It is of great significance to improve the primary productivity of the ocean surface, increase the carbon sink and improve the marine environment. On the basis of the research on the existing artificial upward flow of the gas force, the increase of the flow rate and the increase of the depth of the deep water body are of great significance to the improvement of the marine surface primary productivity. The first is to study the influence of the following parameters on the flow of the artificial upwelling. One is to study the type of gas injection head, two is to study the number of gas injection holes in the gas injection head, the three is to study the depth of gas injection, and the four is to study the type of piping. Then, the influence of the two parameters on the diffusion range of the deep water body is studied, the first is the velocity of the deep water body ejecting from the pipe mouth. Degree, two is the upwelling tube type. In view of the above research tasks, the main use of CFD numerical simulation method is studied and the work flow is as follows. First, the Qiandao Lake experiment of the team members has been carefully studied and analyzed. According to the situation of the Qiandao Lake test, the full scale upwelling tube geometry model and the computational domain geometric model are set up in the business. In the software STAR-CCM+, the grid is divided and the VOF method is used to simulate the artificial upflow of the air force. Two is to verify the correctness and reliability of the calculation results. The first step is to verify the independence of the grid, and use the grid number of 1 million 50 thousand, 1 million 210 thousand, 1 million 530 thousand and 189 million grids to calculate the flow of the deep water under different gas injection quantities, and the final selection is to be selected. The grid number is 1 million 530 thousand as a follow-up grid. The second step is to compare the flow of deep water with the CFD numerical calculation and the experimental data. The trend of the experimental data is basically consistent with the numerical calculation results. Three is to calculate the different gas injection head types using the verified CFD numerical model and the grid. Ring injection gas injection head), different injection holes (24 holes and 384 holes), different gas injection depth (6.1m, 9.6m, 16.1m), different surge pipe type (top dilated tube and top shrinkage tube) in the deep water body to improve the flow. Four is for the deep water diffusion of the study to reestablish the upwelling pipe (equal diameter pipe, top dilatation tube, top contracting tube) and The computational domain geometry model is used in the commercial software STAR-CCM+ to mesh and use the VOF method to calculate the diffusion range of the deep water body. According to the above work process, the following results are completed. First, the ring injection nozzle can increase the depth of the deep water body more than the cross injection head. Two, when the number of holes is 24 holes, it is raised. The flow rate of deep water body is greater than that of 384 holes. Three is the increase of the depth of water with the increase of gas injection depth. Four when the top diameter of the top tube is 0.6m and 0.8m, it can increase the deep water body more than the equal diameter (0.4m diameter) tube, but it is the deep water flow of its elevation when the diameter of the top is 1.0m. At the top of the contraction tube (the top diameter is 0.3m, 0.2m, 0.15m), the depth of the water flow is less than that of the equal diameter tube. Five is the increase of the ejection velocity and the diffusion range under the condition of the equal diameter tube and the top dilatation tube, and the diffusion range is increased with the increase of the ejection velocity at the top of the retraction tube. Six is basically the same. In the case of the same ejection speed, the largest diffusion range is the top dilatation tube, followed by the equal diameter tube, and the minimum range is the top shrinkage tube. Analysis above results show that in the gas injection design of the upwelling pipe, the effect of gas injection from the vicinity of the upwelling tube wall will be better than that from the middle of the upwelling pipe. The number of gas injection corresponds to the size of the blowhole, which is the size of the bubble, and the small bubbles are not conducive to the promotion of deep water body; the depth of gas injection is beneficial to the promotion of deep water body, but this will increase the difficulty of the engineering, and can be adjusted according to the actual conditions of the actual air force artificial upwelling system. Properly expanding the diameter of the upwelling pipe above the gas injecting nozzle can not only increase the flow rate of the deep water body, but also be beneficial to the diffusion of the deep water body.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P74

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