Basic Study On Flow Field Characteristics Of Temperature Difference Liquid Lifting System In Closed Environment

Artificial upwelling technology is an effective technique which can improve marine environment and enrich fishery resources.The temperature differential liquid lifting system mainly produces the reverse vertical temperature gradient by heating method to form the artificial upwelling.In this paper,the basic characteristics of artificial upwelling in closed environment are studied by a series of experimental and numerical simulation methods.It is hoped that the research in this paper will contribute to the exploitation of marine resources and the improvement of marine environment in China.In this paper,the technical characteristics and development status of various artificial upwelling technologies are discussed and summarized from the research background.Then the experimental platform based on PIV system is built for the research of temperature differential liquid hoisting system in closed environment.Through a series of experiments,the flow field characteristics of liquid lifting system in vertical pipe are preliminarily studied,and it is found that the flow in the pipe is still mainly turbulent.The second-rising high-speed water mass pushed the pipe upwelling to continue.The relationship between the characteristic parameters of vertical tube such as pipe diameter,placement position and flow field characteristics is also discussed.The results show that when the diameter of the pipe is equal,the flow velocity is basically the same and the 40mm is 8 m under the conditions of 8mm and 40mm from the bottom of the lower pipe.In the case of m,both the peak velocity and the height of the stationary velocity are delayed.At the same height,the larger the diameter of the pipe,the faster the characteristic rise at the same height.Then the numerical simulation is carried out based on the model reference of the experimental system.The characteristics of the upwelling flow field in different conditions are studied and the influence of heating power,initial temperature and diameter on the upwelling characteristics is investigated.In general,the numerical simulation results are basically the same as the experimental results,which shows the rationality of the numerical model.The characteristic rising velocity of the upwelling flow in the pipe increases first and then decreases with the increase of the height,and then the extreme diffusion occurs at the entrance of the pipe.The upward flow can be divided into stabilization zone,deceleration zone and growth rate according to the variation of the rising characteristic velocity.Three zones.In a certain range,with the increase of pipe diameter,the characteristic velocity tends to stabilize at a higher height.At the same height,the value of characteristic velocity is relatively large under the condition of large pipe diameter.When other conditions are the same,there is a significant positive correlation between the system lift flow and heating power.Although the relative position of the pipe(the height of the bottom surface)has little effect on the flow rate of the pipe,the overall correlation is still positive.Finally,the theoretical model of the closed ambient temperature differential liquid lifting system is explored in this paper.Based on the mathematical analysis of the results obtained from the above numerical simulation,the functional relationship between the nozzle flow rate and the heating power,the initial temperature and the pipe diameter is obtained.In general,through the data processing of the research results,under the studied conditions,the rising velocity of the flow field in the pipe is positively correlated with the heating power,the diameter of the pipe and the height of the pipe,and the flow rate at the outlet of the pipe is related to the heating power.The diameter of the pipe is also positively correlated with the height of the pipe,through the Origin function.After a single variable fitting,the flow rate at the nozzle and initial temperature,pipe diameter and heating power are all quadratic function and cubic function with multivariable.