水幕导流体液膜封闭特性数值模拟
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摘要
为解决水幕液膜所存在的不封闭现象问题,使用FLOW-3D软件,采用RNGκ-ε湍流模型、VOF方法和单相流体模拟水幕导流体液膜流动,应用GMRES方法求解离散方程。通过模拟计算分析"导流体"使液膜达到连续封闭要求的可行性,并分析单宽流量、水箱宽度及导流体间距对液膜流速和厚度的影响。结果表明,通过引入"导流体"可以使液膜达到连续封闭的要求,并根据Nusselt关联式得出了符合自身情况的关联式。
The given paper is aimed at making an introduction of the so-called"flow deflectors"to solve the problem of discontinuous water film. As is known,in daily use,it is often the case with the shrinkage of the water film in the breadth due to the overflow. To solve the trouble,we have managed to work out the corresponding boundary conditions and established a model according to the principle of the experimental devices by CFD software and set up the minimum size of the grid is 0. 25 mm × 0. 25 mm ×0. 25 mm. At the same time,we have also investigated and examined the film model under ten different working conditions under the impact of the three different influential factors. Furthermore,we have also managed to simplify the calculation model according to the actual situation and a series of assumptions. However,the main work we have done is to make a simulated study of the flow of the water film with the flow deflectors by using the FLOW-3 D software,whereas we have solved the discrete equations by using the GMRES method,the RNG κ-ε turbulence model,the VOF method and the single-phase fluid method. According to the simulation results,it has been confirmed that the flow enters a stable state 3 s later. Furthermore,we have also analyzed and proved the feasibility to formulate a continuous airtight water film by the flow deflectors. And,finally,we have gained the influence of the unit breadth flux,the tank breadth and the distance between the flow deflectors on the flowing velocity and thickness of the liquid film through the aforementioned analyses of the distribution curves of the velocity and thickness. The results of our study indicate that the water film under study is well kept in a continuous and airtight status-in-situ with the flow deflectors.And,accordingly,we have also made an assumption of the changing regularity of the water film in the unit breadth flux and the correlation formula according to Nusselt correlation,though the tank width itself has little effect on the water film. Nevertheless,the " dry zones" can also be noticed on the film itself when the distance between the flow deflectors is extended,which implies it is necessary to increase the unit breadth flux to get rid of such zones.
The given paper is aimed at making an introduction of the so-called"flow deflectors"to solve the problem of discontinuous water film. As is known,in daily use,it is often the case with the shrinkage of the water film in the breadth due to the overflow. To solve the trouble,we have managed to work out the corresponding boundary conditions and established a model according to the principle of the experimental devices by CFD software and set up the minimum size of the grid is 0. 25 mm × 0. 25 mm ×0. 25 mm. At the same time,we have also investigated and examined the film model under ten different working conditions under the impact of the three different influential factors. Furthermore,we have also managed to simplify the calculation model according to the actual situation and a series of assumptions. However,the main work we have done is to make a simulated study of the flow of the water film with the flow deflectors by using the FLOW-3 D software,whereas we have solved the discrete equations by using the GMRES method,the RNG κ-ε turbulence model,the VOF method and the single-phase fluid method. According to the simulation results,it has been confirmed that the flow enters a stable state 3 s later. Furthermore,we have also analyzed and proved the feasibility to formulate a continuous airtight water film by the flow deflectors. And,finally,we have gained the influence of the unit breadth flux,the tank breadth and the distance between the flow deflectors on the flowing velocity and thickness of the liquid film through the aforementioned analyses of the distribution curves of the velocity and thickness. The results of our study indicate that the water film under study is well kept in a continuous and airtight status-in-situ with the flow deflectors.And,accordingly,we have also made an assumption of the changing regularity of the water film in the unit breadth flux and the correlation formula according to Nusselt correlation,though the tank width itself has little effect on the water film. Nevertheless,the " dry zones" can also be noticed on the film itself when the distance between the flow deflectors is extended,which implies it is necessary to increase the unit breadth flux to get rid of such zones.
引文
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[10]BAO Zhongjin(包中进),WANG Yuehua(王月华).Three-dimensional numerical simulation of spillway based on FLOW-3D[J].Zhejiang Hydrotechnics(浙江水利科技),2012(2):5-9.
[11]WANG Qing(王青),HUANG Xibin(黄细彬).Three-dimensional numerical simulation of flow in bend of steep slope based on FLOW-3D[J].Journal of Water Resources&Water Engineering(水资源与水工程学报),2016,27(5):145-149.
[12]SONG Yongjia(宋永嘉),LI Shuangjiang(李双江),BA Chao(巴超).Hydraulic cascade simulation test of landscape waterfall based on FLOW-3D[J].China Rural Water and Hydropower(中国农村水利水电),2013(7):147-148.
[13]ZHENG Li(郑力),QIAN Zhongdong(钱忠东),CAO Zhixian(曹志先),et al.Comparison of computed result for dam overtoppingflow with two 3D models[J].Engineering Journal of Wuhan University:Engineering Edition(武汉大学学报:工学版),2009,42(6):758-763.
[14]HIRT C W,NICHOLS B D.Volume of fluid(VOF)method for the dynamics of free boundaries[J].Journal of Computational Physics,1981,39(1):201-225.
[15]HARTLEY D E,MURGATROYD W.Criteria for the break-up of thin liquid layers flowing isothermally over solid surfaces[J].International Journal of Heat and Mass Transfer,1964,7(9):1003-1015.
[16]QIN Wei(秦伟),LIU Jianhua(刘建华),WENG Zemin(翁泽民),et al.Characteristics of interfacial surface wave of free-falling liquid film[J].Journal of Jimei Navigation Institute(集美航海学院学报),1997,15(2):3-8.
[17]YE X,YAN W,JIANG Z,et al.Hydrodynamics of free-falling turbulent wavy films and implications for enhanced heat transfer[J].Heat Transfer Engineering,2002,23(1):48-60.
[2]WANG Chuanzheng(王传正).Application of the water screen for fire prevention and smoke insulation during underground structures on fire[J].Journal of Wuhan Iron and Steel University(武汉钢铁学院学报),1994,17(2):224-229.
[3]WANG Jinghua(王靖华),MAO Genhai(毛根海),CHEN Shaoqing(陈少庆),et al.Experimental study on hydraulic design of artificial waterfall[J].Water&Wastewater Engineering(给水排水),2001,27(5):59-61.
[4]LIU Yufeng(刘玉峰),TONG Yijun(童一峻),REN Haigang(任海刚),et al.Numerical investigation on flow characteristics of falling water filmdown a vertical plate at high reynolds number[J].Infrared Technology(红外技术),2010,32(10):567-571.
[5]SABER H H,EL-GENK M S.On the breakup of a thin liquid film subject to interfacial shear[J].Journal of Fluid Mechanics,2004,500:113-133.
[6]GONG H,JIANG J,QIU J,et al.Theoretical and experimental study on the water curtain shape and mechanical relationship of the smoke control system[C]//International Symposium on Mechanical Engineering and Material Science(ISMEMS 2016).Jeju-si:Atlantis Press.2016:500-507.
[7]HO C,CHANG H,CHEN H,et al.CFD simulation of the twophase flow for a falling film microreactor[J].International Journal of Heat and Mass Transfer,2011,54(15/16):3740-3748.
[8]LUO L,ZHANG G,PAN J,et al.Flow and heat transfer characteristics of falling water film on horizontal circular and non-circular cylinders[J].Journal of Hydrodynamics,2013,25(3):404-414.
[9]WANG Yuehua(王月华),BAO Zhongjin(包中进),WANG Bin(王斌).Three-dimensional numerical simulation of flow in stilling basin based on flow-3d[J].Engineering Journal of Wuhan University:Engineering Edition(武汉大学学报:工学版),2012,45(4):454-457.
[10]BAO Zhongjin(包中进),WANG Yuehua(王月华).Three-dimensional numerical simulation of spillway based on FLOW-3D[J].Zhejiang Hydrotechnics(浙江水利科技),2012(2):5-9.
[11]WANG Qing(王青),HUANG Xibin(黄细彬).Three-dimensional numerical simulation of flow in bend of steep slope based on FLOW-3D[J].Journal of Water Resources&Water Engineering(水资源与水工程学报),2016,27(5):145-149.
[12]SONG Yongjia(宋永嘉),LI Shuangjiang(李双江),BA Chao(巴超).Hydraulic cascade simulation test of landscape waterfall based on FLOW-3D[J].China Rural Water and Hydropower(中国农村水利水电),2013(7):147-148.
[13]ZHENG Li(郑力),QIAN Zhongdong(钱忠东),CAO Zhixian(曹志先),et al.Comparison of computed result for dam overtoppingflow with two 3D models[J].Engineering Journal of Wuhan University:Engineering Edition(武汉大学学报:工学版),2009,42(6):758-763.
[14]HIRT C W,NICHOLS B D.Volume of fluid(VOF)method for the dynamics of free boundaries[J].Journal of Computational Physics,1981,39(1):201-225.
[15]HARTLEY D E,MURGATROYD W.Criteria for the break-up of thin liquid layers flowing isothermally over solid surfaces[J].International Journal of Heat and Mass Transfer,1964,7(9):1003-1015.
[16]QIN Wei(秦伟),LIU Jianhua(刘建华),WENG Zemin(翁泽民),et al.Characteristics of interfacial surface wave of free-falling liquid film[J].Journal of Jimei Navigation Institute(集美航海学院学报),1997,15(2):3-8.
[17]YE X,YAN W,JIANG Z,et al.Hydrodynamics of free-falling turbulent wavy films and implications for enhanced heat transfer[J].Heat Transfer Engineering,2002,23(1):48-60.