养殖网箱周围流场特性的三维数值模拟
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摘要
近年来,由于人口的增加,对水产品的需求增大,近海水产资源日趋枯竭。再加上过度捕捞和不合理的开发利用等因素影响,近海生态环境逐渐恶化。因此,把网箱养殖转移到外海,寻求优越的养殖环境以及高质量的养殖产品成为网箱养殖发展的必然趋势,深水养殖网箱应运而生。在深水网箱养殖过程中,箱内水体的流动与鱼类生长密切相关。在网箱水动力数值计算中,网衣的减流效应同样受到关注。因此,对网衣周围流场特性的研究有着重要意义,研究成果将对网箱养殖的生产实践起到积极的指导作用。网衣属于柔性小尺度、大变形、多孔结构,利用数值方法来实现其周围流场的模拟难度很大,目前,在网箱流场方面的研究成果大多数是采用物理模型试验和现场测量的方法,数值模拟方面的研究较少。
本文采用Realizable k-ε湍流模型,结合多孔介质模型模拟网衣,建立了模拟水流作用下平面网衣周围流场的数值模型。利用最小二乘法分析作用在平面网衣上的水流力与流速和冲角的关系,得到对应的多孔介质系数,使得多孔介质区域具有与网衣相同的阻水效果。运用该数值模型对网衣及网箱周围流场特性进行数值模拟研究,获得较好效果。
论文主要内容分为五章：第一章是绪论,简要介绍了课题背景和网箱流场方面的研究进展。第二章介绍了建立多孔介质模型的数值方法,主要包括控制方程、多孔介质系数、边界条件及网格划分和数值计算方法等。第三章为数值模拟及试验验证,首先采用本文提出的数学模型对平面网衣和方形网箱进行二维数值模拟,并通过模型试验进行验证。在此基础上,对不同冲角和流速条件下的平面网衣周围流场进行了三维数值模拟,并通过模型进行验证。第四章为平面网衣周围流场的数值模拟,本章对网衣倾角、高度、间距和数目等参数在一定范围内变化时,对平面网衣周围流场产生的影响进行了研究。第五章为网箱周围流场的数值模拟,在对平面网衣周围流场准确模拟的基础上,将网箱模型简化为由若干平面网衣组成,从而利用本文模型对整体网箱周围流场进行数值模拟,并对单体网箱以及组合网箱周围流场特性进行了研究。
In recent years, the fishing stock is decreasing because the demand for fish production has grown substantially as the world's population increase. On the other hand, the ecological environment of near-shore locations becomes worse and worse due to overfishing and excess exploitation. Because of the consideration of fish farming environment and high quality fish food, more and more net cages for aquaculture will be located offshore and the deep-water cage arises at the historic moment. In a deep-water cage, water flow within the net cage is closely related to the fish growth. The flow velocity reduction effect behind the fishing net is a major concern. Thus, the investigation on the flow field around the cage net has become an important subject. The research results will play a positive role in guiding the production practice of fish farming. The fishing net is a kind of small-scale flexible structure, the numerical study on flow field around the net structure is rather complex. At present, the efforts on the flow field around the net cage are mainly concentrated on physical model tests and field measurements and numerical simulation research is relatively rare.
A numerical model combined the Realizable k-ε turbulence model and the porous media model is established to simulate the flow field around cage net under current. The unknown porous coefficients are determined from the experimental forces on the net and flow velocities and the angles of attack using the least square method. Therefore, the porous media act the same water-blocking effect as the net. This numerical model is applied for the simulation of the flow field around the plane net and the net cage under current and the numerical results are satisfactory.
The contents are mainly composed of five chapters. The first chapter gives a general description on the background of the subject and the development of researches on flow field around net cages. The second chapter is the numerical method of the porous media model including the governing equations, porous media resistance coefficients, mesh grids and boundary conditions, numerical algorithm method. The third chapter is the experimental verifications. Firstly a two dimensional numerical model is applied for modeling the flow field around a net panel and a square cage under current and the numerical results are compared with data obtained by physical model tests. On this basis, a three dimensional numerical model is applied for modeling the flow field around a net panel at different attack angles and velocities, which is verified by physical model tests. In the fourth chapter, the flow field around a plane net with different plane net inclination angles, plane net heights, spacing distances between two plane nets and plane net numbers are presented and the effects of these parameters on the flow field around the plane net are investigated. The fifth chapter is the numerical simulation of the flow field around net cages. Based on the simulation of the flow field around plane net, the flow field inside and around a gravity cage can be simulated by dividing the net cage into many plane nets with different attack angle. Therefore, the simulation of the flow field inside and around a gravity cage is straight forward and the flow fields inside and around single gravity cage and composite-type net cages are investigated.
本文采用Realizable k-ε湍流模型,结合多孔介质模型模拟网衣,建立了模拟水流作用下平面网衣周围流场的数值模型。利用最小二乘法分析作用在平面网衣上的水流力与流速和冲角的关系,得到对应的多孔介质系数,使得多孔介质区域具有与网衣相同的阻水效果。运用该数值模型对网衣及网箱周围流场特性进行数值模拟研究,获得较好效果。
论文主要内容分为五章：第一章是绪论,简要介绍了课题背景和网箱流场方面的研究进展。第二章介绍了建立多孔介质模型的数值方法,主要包括控制方程、多孔介质系数、边界条件及网格划分和数值计算方法等。第三章为数值模拟及试验验证,首先采用本文提出的数学模型对平面网衣和方形网箱进行二维数值模拟,并通过模型试验进行验证。在此基础上,对不同冲角和流速条件下的平面网衣周围流场进行了三维数值模拟,并通过模型进行验证。第四章为平面网衣周围流场的数值模拟,本章对网衣倾角、高度、间距和数目等参数在一定范围内变化时,对平面网衣周围流场产生的影响进行了研究。第五章为网箱周围流场的数值模拟,在对平面网衣周围流场准确模拟的基础上,将网箱模型简化为由若干平面网衣组成,从而利用本文模型对整体网箱周围流场进行数值模拟,并对单体网箱以及组合网箱周围流场特性进行了研究。
In recent years, the fishing stock is decreasing because the demand for fish production has grown substantially as the world's population increase. On the other hand, the ecological environment of near-shore locations becomes worse and worse due to overfishing and excess exploitation. Because of the consideration of fish farming environment and high quality fish food, more and more net cages for aquaculture will be located offshore and the deep-water cage arises at the historic moment. In a deep-water cage, water flow within the net cage is closely related to the fish growth. The flow velocity reduction effect behind the fishing net is a major concern. Thus, the investigation on the flow field around the cage net has become an important subject. The research results will play a positive role in guiding the production practice of fish farming. The fishing net is a kind of small-scale flexible structure, the numerical study on flow field around the net structure is rather complex. At present, the efforts on the flow field around the net cage are mainly concentrated on physical model tests and field measurements and numerical simulation research is relatively rare.
A numerical model combined the Realizable k-ε turbulence model and the porous media model is established to simulate the flow field around cage net under current. The unknown porous coefficients are determined from the experimental forces on the net and flow velocities and the angles of attack using the least square method. Therefore, the porous media act the same water-blocking effect as the net. This numerical model is applied for the simulation of the flow field around the plane net and the net cage under current and the numerical results are satisfactory.
The contents are mainly composed of five chapters. The first chapter gives a general description on the background of the subject and the development of researches on flow field around net cages. The second chapter is the numerical method of the porous media model including the governing equations, porous media resistance coefficients, mesh grids and boundary conditions, numerical algorithm method. The third chapter is the experimental verifications. Firstly a two dimensional numerical model is applied for modeling the flow field around a net panel and a square cage under current and the numerical results are compared with data obtained by physical model tests. On this basis, a three dimensional numerical model is applied for modeling the flow field around a net panel at different attack angles and velocities, which is verified by physical model tests. In the fourth chapter, the flow field around a plane net with different plane net inclination angles, plane net heights, spacing distances between two plane nets and plane net numbers are presented and the effects of these parameters on the flow field around the plane net are investigated. The fifth chapter is the numerical simulation of the flow field around net cages. Based on the simulation of the flow field around plane net, the flow field inside and around a gravity cage can be simulated by dividing the net cage into many plane nets with different attack angle. Therefore, the simulation of the flow field inside and around a gravity cage is straight forward and the flow fields inside and around single gravity cage and composite-type net cages are investigated.
引文
[1]赵云鹏.深水重力式网箱水动力特性数值模拟研究[D].大连理工大学,2007.
[2]李玉成.海洋工程技术进展与对发展我国海洋经济的思考[J].大连理工大学学报,2002,42(1)：1-5.
[3]桂福坤,王炜霞,张怀慧.网箱工程发展现状及展望[J].大连水产学院学报,2002,17(1)：70-78.
[4]徐君卓.深水网箱养鱼业的现状及发展趋势[J].海洋渔业,2004,26(3)：225-230.
[5]陈昌平,李玉成,赵云鹏,等.波流共同作用下单体网格式锚碇网箱水动力特性研究[J].水动力学研究与进展A辑,2009,24(4)：493-502.
[6]CHEN C P, LI Y C, ZHAO Y P, et al. Numerical analysis on effects of submerged depth of the grid and direction of incident wave on gravity cage [J]. China Ocean Engineering,2009,23(2): 233-250.
[7]陈昌平,李玉成,赵云鹏,等.波流入射方向对网格式锚碇网箱水动力特性的影响[J].中国水产科学,2010,17(4)：828-838.
[8]ZHAO Y P, LI Y C, DONG G H, et al. Numerical simulation of hydrodynamic behaviors of gravity cage in waves [J]. China Ocean Engineering,2007,21(2):225-238.
[9]董华洋,王永学,侯勇,等.矩形箱式浮防波堤水动力特性试验研究[J].渔业现代化,2009,36(3)：7-11.
[10]ZHAO Y P, LI Y C, DONG G H, et al. An experimental and numerical study of hydrodynamic characteristics of submerged flexible plane nets in waves [J]. Aquacultural Engineering,2008, 38(1):16-25.
[11]DONG G H, XU T J, ZHAO Y P, et al. Numerical simulation of hydrodynamic behavior of gravity cage in irregular waves [J]. Aquacultural Engineering,2010,42(2):90-101.
[12]赵云鹏.深水重力式网箱水动力特性数值模拟研究[J].渔业现代化,2011,38(2)：10-16.
[13]WAN R, HU F X, TOKAI T A. Static analysis of the tension and configuration of submerged plane nets [J]. Fisheries Science,2002,68(4):815-823.
[14]LADER P F, ENERHAUG B. Experimental investigation of forces and geometry of a net cage in uniform flow [J]. IEEE Journal of Oceanic Engineering,2005,30(1):79-84.
[15]HUANG C C, TANG H J, LIU J Y. Dynamical analysis of net cage structures for marine aquaculture:Numerical simulation and model testing [J]. Aquacultural Engineering,2006,35(3): 258-270.
[16]滕斌,郝春玲,郑艳娜.波流作用下深水网箱动力响应数值模拟的初析[C].第一届海洋生物高技术论坛论文集(上册),舟山,2003：387-392.
[17]宋芳.碟形和拟碟形深水网箱的水动力特性的实验研究[D].大连理工大学,2003.
[18]GUI F K, LI Y C, ZHAO Y P, DONG G H. A model for the calculation of velocity reduction behind a plane fishing net [J]. China Ocean Engineering,2006,20(4):615-622.
[19]TSUKROV I, EROSHKIN O, FREDRIKSSON D W, et al. Finite element modeling of net panels using a consistent net element [J]. Ocean Eng.,2003,30(2),251-270.
[20]苏炜,詹杰民.等效网面法在模型网的水动力特性中的应用[J].水动力学研究与进展A辑,2007,22(3)：267-272.
[21]AARNSES J, RUDI H, LΦLAND G. Current forces on cage, net deflection [C]. Proceedings of a conference organised by the Institution of Civil Engineers, Glasgow, UK,17-18 October,1990, 137-152.
[22]李惠礼,柳学周.海况条件对海水养殖网箱性能的影响.海洋水产研究,1999,20(1)：57-63.
[23]FREDRIKSSON D W. Open ocean fish cage and mooring system dynamics [D]. Durham, NH, USA:University of New Hampshire,2001.
[24]LADER P F, ENERHAUG B, FREDHEIM A, et al. Modelling of 3D net structures exposed to wave and current [C]. In:3rd International Conference on Hydroelasticity in Marine Tecnology, 2003:19-26.
[25]李玉成,陈昌平,李春柳,等.重力式网箱阻流效应的研究[J].中国造船,2005,46(z1)：105-109.
[26]陈昌平.深水网格式锚碇网箱水动力特性研究[D].大连：大连理工大学,2010.
[27]JOHANSSON D, JUELL J E, OPPEDAL F, et al. The influence of the pycnocline and cage resistance on current flow, oxygen flux and swimming behaviour of Atlantic salmon (Salmo salar L) in production cages [J]. Aquaculture.2007,265(1):271-287.
[28]HARENDZA A, VISSCHER J, GANSEL L, et al. PIV on inclined cylinder shaped fish cages in a current and the resulting flow field [C]. In:27th International Conference on Offshore Mechanics and Arctic Engineering, Estoril, Portugal,2008, OMAE2008-57748.
[29]GANSEL L, RACKEBRANDT S, OPPEDAL F, et al. Flow fields inside stocked fish cage and the near environment [C]. In:30th International Conference on Offshore Mechanics and Arctic Engineering, Rotterdam, Netherlands,2011, OMAE2011-50205.
[30]PATURSSON Φ. Tow tank measurements of drag and lift force on a net panel and current reduction behind the net panel [R]. New Hampshire, USA:Technical Report NVDRit 2007, 2007.
[31]黄六一,梁振林,宋伟华,等.方形网箱结构减流效果试验[J].中国水产科学,2007,14(5)：860-863.
[32]宋伟华,马家志,吕永林,等.方形网箱减流效果的试验与应用[J].浙江海洋学院学报(自然科学版),2007,26(4)：378-383.
[33]桂福坤.深水重力式网箱水动力学特性研究[D].大连理工大学,2006.
[34]BOUHOUBEINY E, GERMAIN G, DRUAULT P. Time-resolved PIV investigations of the flow field around cod-end net structures [J]. Fisheries Research,2011,108(2-3):344-355.
[35]ENERHAUG B, GJ0SUND S H, HANSEN K. Experimental, numerical and analytical studies of flow through reticulate and solid cones [C]. In:Proceedings of the 5th international workshop on methods for the development and evaluation of maritime technologies. Rostock, Germany,2001, vol.2,43-59.
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[42]赵云鹏,毕春伟,董国海,李玉成.平面网衣周围流场的三维数值模拟[J].水动力学研究与进展A辑,2011年,26(5)：606-613.
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[2]李玉成.海洋工程技术进展与对发展我国海洋经济的思考[J].大连理工大学学报,2002,42(1)：1-5.
[3]桂福坤,王炜霞,张怀慧.网箱工程发展现状及展望[J].大连水产学院学报,2002,17(1)：70-78.
[4]徐君卓.深水网箱养鱼业的现状及发展趋势[J].海洋渔业,2004,26(3)：225-230.
[5]陈昌平,李玉成,赵云鹏,等.波流共同作用下单体网格式锚碇网箱水动力特性研究[J].水动力学研究与进展A辑,2009,24(4)：493-502.
[6]CHEN C P, LI Y C, ZHAO Y P, et al. Numerical analysis on effects of submerged depth of the grid and direction of incident wave on gravity cage [J]. China Ocean Engineering,2009,23(2): 233-250.
[7]陈昌平,李玉成,赵云鹏,等.波流入射方向对网格式锚碇网箱水动力特性的影响[J].中国水产科学,2010,17(4)：828-838.
[8]ZHAO Y P, LI Y C, DONG G H, et al. Numerical simulation of hydrodynamic behaviors of gravity cage in waves [J]. China Ocean Engineering,2007,21(2):225-238.
[9]董华洋,王永学,侯勇,等.矩形箱式浮防波堤水动力特性试验研究[J].渔业现代化,2009,36(3)：7-11.
[10]ZHAO Y P, LI Y C, DONG G H, et al. An experimental and numerical study of hydrodynamic characteristics of submerged flexible plane nets in waves [J]. Aquacultural Engineering,2008, 38(1):16-25.
[11]DONG G H, XU T J, ZHAO Y P, et al. Numerical simulation of hydrodynamic behavior of gravity cage in irregular waves [J]. Aquacultural Engineering,2010,42(2):90-101.
[12]赵云鹏.深水重力式网箱水动力特性数值模拟研究[J].渔业现代化,2011,38(2)：10-16.
[13]WAN R, HU F X, TOKAI T A. Static analysis of the tension and configuration of submerged plane nets [J]. Fisheries Science,2002,68(4):815-823.
[14]LADER P F, ENERHAUG B. Experimental investigation of forces and geometry of a net cage in uniform flow [J]. IEEE Journal of Oceanic Engineering,2005,30(1):79-84.
[15]HUANG C C, TANG H J, LIU J Y. Dynamical analysis of net cage structures for marine aquaculture:Numerical simulation and model testing [J]. Aquacultural Engineering,2006,35(3): 258-270.
[16]滕斌,郝春玲,郑艳娜.波流作用下深水网箱动力响应数值模拟的初析[C].第一届海洋生物高技术论坛论文集(上册),舟山,2003：387-392.
[17]宋芳.碟形和拟碟形深水网箱的水动力特性的实验研究[D].大连理工大学,2003.
[18]GUI F K, LI Y C, ZHAO Y P, DONG G H. A model for the calculation of velocity reduction behind a plane fishing net [J]. China Ocean Engineering,2006,20(4):615-622.
[19]TSUKROV I, EROSHKIN O, FREDRIKSSON D W, et al. Finite element modeling of net panels using a consistent net element [J]. Ocean Eng.,2003,30(2),251-270.
[20]苏炜,詹杰民.等效网面法在模型网的水动力特性中的应用[J].水动力学研究与进展A辑,2007,22(3)：267-272.
[21]AARNSES J, RUDI H, LΦLAND G. Current forces on cage, net deflection [C]. Proceedings of a conference organised by the Institution of Civil Engineers, Glasgow, UK,17-18 October,1990, 137-152.
[22]李惠礼,柳学周.海况条件对海水养殖网箱性能的影响.海洋水产研究,1999,20(1)：57-63.
[23]FREDRIKSSON D W. Open ocean fish cage and mooring system dynamics [D]. Durham, NH, USA:University of New Hampshire,2001.
[24]LADER P F, ENERHAUG B, FREDHEIM A, et al. Modelling of 3D net structures exposed to wave and current [C]. In:3rd International Conference on Hydroelasticity in Marine Tecnology, 2003:19-26.
[25]李玉成,陈昌平,李春柳,等.重力式网箱阻流效应的研究[J].中国造船,2005,46(z1)：105-109.
[26]陈昌平.深水网格式锚碇网箱水动力特性研究[D].大连：大连理工大学,2010.
[27]JOHANSSON D, JUELL J E, OPPEDAL F, et al. The influence of the pycnocline and cage resistance on current flow, oxygen flux and swimming behaviour of Atlantic salmon (Salmo salar L) in production cages [J]. Aquaculture.2007,265(1):271-287.
[28]HARENDZA A, VISSCHER J, GANSEL L, et al. PIV on inclined cylinder shaped fish cages in a current and the resulting flow field [C]. In:27th International Conference on Offshore Mechanics and Arctic Engineering, Estoril, Portugal,2008, OMAE2008-57748.
[29]GANSEL L, RACKEBRANDT S, OPPEDAL F, et al. Flow fields inside stocked fish cage and the near environment [C]. In:30th International Conference on Offshore Mechanics and Arctic Engineering, Rotterdam, Netherlands,2011, OMAE2011-50205.
[30]PATURSSON Φ. Tow tank measurements of drag and lift force on a net panel and current reduction behind the net panel [R]. New Hampshire, USA:Technical Report NVDRit 2007, 2007.
[31]黄六一,梁振林,宋伟华,等.方形网箱结构减流效果试验[J].中国水产科学,2007,14(5)：860-863.
[32]宋伟华,马家志,吕永林,等.方形网箱减流效果的试验与应用[J].浙江海洋学院学报(自然科学版),2007,26(4)：378-383.
[33]桂福坤.深水重力式网箱水动力学特性研究[D].大连理工大学,2006.
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