温度分层及水深对扬水曝气器流场影响的CFD模拟
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摘要
扬水曝气是为解决大水深水库水体富营养化、底泥内源污染物释放等问题而开发的新型水质原位修复改善技术。扬水曝气器通过间歇性的气弹向水体充氧提高底部溶解氧改变下层水体的厌氧状态,控制底泥中的氮、磷、铁、锰、有机物向水体释放。通过曝气造成水体上下层之间混合,破坏大水深水体的温度分层现象,并可使表层藻类向下迁移至无光区域,从而抑制藻类的生长,最终致其死亡。
计算流体力学(CFD)技术利用离散化的数值方法和计算机,通过求解描述流体运动的质量守恒方程、动量守恒方程和能量守恒方程,对复杂的流体流动进行数值模拟和系统分析。通过CFD数值模拟,可以方便地得到复杂流场内不同位置、不同时刻的基本物理量(如温度、速度、压力、浓度等)的数值和变化情况。本论文中采用目前功能最全面、使用最广泛的CFD软件—Fluent进行模拟计算。
本论文通过使用Fluent软件模拟大水深水库温度分层、水深对扬水曝气器外围流场的影响,得到以下主要结论：
(1)温度分层对于扬水曝气器稳定工作后形成除藻区域所占比例影响不大,无论夏季还是冬季工况,除藻区域所占比例基本稳定在75%左右。水库表层与底部温差大时,流场中漩涡的形成所需时间会比较长。当水库表层与底部温差相同时,斜温层的位置越深,流场中漩涡中心就越靠近水库底部。
(2)在同样的作用半径、气弹周期和出口流速条件下,扬水曝气器工作时在大水深时形成稳定流场所需时间会大大增大,但在稳定的流场中除藻区域分布形式大致相同,除藻区域所占比例也基本相同。
(3)利用Fluent的绘制质点迹线功能,可分析藻类在扬水曝气器稳定工作形成的流场中流动情况。藻类随漩涡流动,其在无光的衰亡区域流行时间远大于在生产区域的流行时间,经多次循环,藻类不断消耗自身的有机质,最终死亡。模拟结果表明扬水曝气器对藻类生长有抑制作用。
(4)水深增大,藻类在无光的衰亡区域流行时间会增大,扬水曝气器的除藻效率会提高。但同时曝气器出口流动对流场的搅动作用就会相应降低,而且,大水深时产生气弹要克服的阻力大,扬水曝气器工作时所需动力就会增大,扬水曝气器的运行费用会增高。因此,宜综合考虑除藻效率和运行成本来选择扬水曝气器的布置地点。
The Ware-lifting Aerator, aiming at solving water quality problems of eutrophication and pollutants'releasing from sediments in deep reservoirs, is a new water quality improvement device. By mixing water or oxygenating water directly, the aerator can improve and change the anaerobic state in the lower waters, which can control the pollutants'(such as nitrogen, phosphorus, iron, manganese, organic materials) releasing from sediment into the water body. By aerating, the waters in the upper-layer and lower-layer can be mixed, the thermal stratification can be destructed, and algae can then be brought down to the lower-layer where algae would die finally because of no light.
With the help of the discretization method and the computer, the continuous equation, momentum equation and energy equation can be solved by Computational Fluid Dynamics (CFD) simulation, and complex flow motion can be numerically simulated and analysed. Using CFD simulation, the basic physical parameters (such as temperature, velocity, pressure, concentration) can be easily predicted at different locations and times. As a powerful computing package, FLUENT was employed to simulate the complex motions of air and water.
Through the Fluent simulation, the effects of thermal stratification and water depth on the flow field around Water-lifting Aerator were investigated and the main conclusions were as follows:
(1) Whether in the summer or winter, thermal stratification had little effect on the area without algae when the aerator worked stably, and the proportion of area without algae retained about 75%. If the temperature difference between the surface and bottom of the reservoir was noticeable, the time of developing the eddy zone was long. If the temperatures on the surface and bottom of the reservoir were the same, the deeper the thermocline layer, the nearer the eddy zone to the reservoir bottom.
(2)Under the same conditions of affecting radius, gas shell period and outflow velocity, the time for steady flow development was long when the Water-lifting Aerator worked under the deep water condition. However, the proportions of area without area retained same.
(3)Using Fluent's function of tracing flow, the algae motion in the reservoir can be analyzed when the water-lifting aerator worked stably. Gong with the water flow, algae stayed in the decay area longer than in the production area. After several times of circulation, algae continued to consume their own organic materials and died ultimately.
(4)If the water depth increases, the time of algae's flowing through the decay area will increase, algae removal efficiency will increase. However, the stirring effect of outlet flow will be weakened accordingly, larger flow resistance will be overcome to develop gas shells, more energy will be required and the Water-lifting Aerator's running costs will be higher. Therefore, comprehensive consideration of algae removal efficiency and operating costs should be given to select the optimum layout of the Water-lifting Aerator in the reservoir.
计算流体力学(CFD)技术利用离散化的数值方法和计算机,通过求解描述流体运动的质量守恒方程、动量守恒方程和能量守恒方程,对复杂的流体流动进行数值模拟和系统分析。通过CFD数值模拟,可以方便地得到复杂流场内不同位置、不同时刻的基本物理量(如温度、速度、压力、浓度等)的数值和变化情况。本论文中采用目前功能最全面、使用最广泛的CFD软件—Fluent进行模拟计算。
本论文通过使用Fluent软件模拟大水深水库温度分层、水深对扬水曝气器外围流场的影响,得到以下主要结论：
(1)温度分层对于扬水曝气器稳定工作后形成除藻区域所占比例影响不大,无论夏季还是冬季工况,除藻区域所占比例基本稳定在75%左右。水库表层与底部温差大时,流场中漩涡的形成所需时间会比较长。当水库表层与底部温差相同时,斜温层的位置越深,流场中漩涡中心就越靠近水库底部。
(2)在同样的作用半径、气弹周期和出口流速条件下,扬水曝气器工作时在大水深时形成稳定流场所需时间会大大增大,但在稳定的流场中除藻区域分布形式大致相同,除藻区域所占比例也基本相同。
(3)利用Fluent的绘制质点迹线功能,可分析藻类在扬水曝气器稳定工作形成的流场中流动情况。藻类随漩涡流动,其在无光的衰亡区域流行时间远大于在生产区域的流行时间,经多次循环,藻类不断消耗自身的有机质,最终死亡。模拟结果表明扬水曝气器对藻类生长有抑制作用。
(4)水深增大,藻类在无光的衰亡区域流行时间会增大,扬水曝气器的除藻效率会提高。但同时曝气器出口流动对流场的搅动作用就会相应降低,而且,大水深时产生气弹要克服的阻力大,扬水曝气器工作时所需动力就会增大,扬水曝气器的运行费用会增高。因此,宜综合考虑除藻效率和运行成本来选择扬水曝气器的布置地点。
The Ware-lifting Aerator, aiming at solving water quality problems of eutrophication and pollutants'releasing from sediments in deep reservoirs, is a new water quality improvement device. By mixing water or oxygenating water directly, the aerator can improve and change the anaerobic state in the lower waters, which can control the pollutants'(such as nitrogen, phosphorus, iron, manganese, organic materials) releasing from sediment into the water body. By aerating, the waters in the upper-layer and lower-layer can be mixed, the thermal stratification can be destructed, and algae can then be brought down to the lower-layer where algae would die finally because of no light.
With the help of the discretization method and the computer, the continuous equation, momentum equation and energy equation can be solved by Computational Fluid Dynamics (CFD) simulation, and complex flow motion can be numerically simulated and analysed. Using CFD simulation, the basic physical parameters (such as temperature, velocity, pressure, concentration) can be easily predicted at different locations and times. As a powerful computing package, FLUENT was employed to simulate the complex motions of air and water.
Through the Fluent simulation, the effects of thermal stratification and water depth on the flow field around Water-lifting Aerator were investigated and the main conclusions were as follows:
(1) Whether in the summer or winter, thermal stratification had little effect on the area without algae when the aerator worked stably, and the proportion of area without algae retained about 75%. If the temperature difference between the surface and bottom of the reservoir was noticeable, the time of developing the eddy zone was long. If the temperatures on the surface and bottom of the reservoir were the same, the deeper the thermocline layer, the nearer the eddy zone to the reservoir bottom.
(2)Under the same conditions of affecting radius, gas shell period and outflow velocity, the time for steady flow development was long when the Water-lifting Aerator worked under the deep water condition. However, the proportions of area without area retained same.
(3)Using Fluent's function of tracing flow, the algae motion in the reservoir can be analyzed when the water-lifting aerator worked stably. Gong with the water flow, algae stayed in the decay area longer than in the production area. After several times of circulation, algae continued to consume their own organic materials and died ultimately.
(4)If the water depth increases, the time of algae's flowing through the decay area will increase, algae removal efficiency will increase. However, the stirring effect of outlet flow will be weakened accordingly, larger flow resistance will be overcome to develop gas shells, more energy will be required and the Water-lifting Aerator's running costs will be higher. Therefore, comprehensive consideration of algae removal efficiency and operating costs should be given to select the optimum layout of the Water-lifting Aerator in the reservoir.
引文
[1]谯华,周从直,谢有奎.湖泊富营养化的形成机制与防治对策[J].环境科学导刊,2007,26(6)：45-48
[2]朱智,吴江明,周俊杰.滇池污染治理工作若干问题的思考[J].中国给水排水,1999,15(12)：27-30
[3]黄廷林,丛海兵,柴蓓蓓.饮用水水源水质污染控制[M].北京.中国建筑工业出版社.2009：122
[4]Gary J. Jones, Wojciech Poplawski. Understanding and management of Cyanobacterial blooms in sub-tropical reservoirs of Queensland,[J].water science technology,1998,37(2): 161-168
[5]金相灿,荆一凤,刘文生.湖泊污染底泥疏浚技术[J].环境科学研究,1999,12(5)：9-12
[6]Friedrich Recknagel, Masaaki Hosomi, Takehiko Fukushima, et al. Short-and Long-term Control of External and Internal Phosphorus Loads in Lakes——a scenario analysis[J]. Water Research,1995,29(7):1767-1779
[7]Milan Straskraba. Ecotechnological Methods for Managing Non-point Source Pollution in Watersheds, Lakes and Reservoirs[J]. Wat. Sci.Tech,1996,33(4-5):73-80
[8]丛海兵,扬水曝气水源水质改善技术研究[D].西安：西安建筑科技大学,2007.
[9]刘建康,谢平.用鲢鳙直接控制微囊藻水华的围隔试验和湖泊实践[J].生态科学,2003,22(3)：193-196.
[10]罗阳,刘敬.控制湖泊内源磷负荷的有效性研究[J].水资源保护,1996,2：52-55
[11]Petra M.Visser,Henk A.M Ketelaars.Reduced growth of the cyanobacterium microcystis in an artificially mixed lake and reservioir[J].Water science technology,1995,32(4):53-54
[12]Holdren C, W Jones, J Taggart. Managing Lakes and Reservoirs[M].3rd edition Prep. By N. Am. Lake Manage. Soc. And Terrene Inst., in coop, with U. S. EPA.,2001
[13]Murphy T. P., Lawson A., Kumagai M. Review of emerging issue in sediment treatment [J]. Aquatic Ecosystem Health and Management,1999, (2):419-434
[14]Clasen J. Raw water quality management at Wahnbach reservoir [J]. Water supply,2000,18(1):581-585
[15]丛海兵,黄廷林,缪晶广等.水体修复装置——扬水曝气器的开发.[J]中国给水排水,2005, 21(3)：41-45
[16]丛海兵,黄廷林,缪晶广等.扬水曝气器的水质改善功能及提水、充氧性能研究.[J]环境工程学报,2007,1(1)：7-13
[17]丛海兵,黄廷林,赵建伟等.扬水曝气器技术在水源水质改善中的应用.[J]环境污染与防治,2006,28(3)：215-218
[18]朱伟峰,基于CFD的扬水曝气器外围流场及曝气室流场模拟.[D]西安,西安建筑科技大学,2008.
[19]黄廷林,李建军.扬水曝气技术对汾河水库原水水质的改善.[J],供水技术,2007,10：13-16
[20]李素琴.浅谈汾河水库水质的改善.[J],科技情报开发与经济,2007,17：251-252
[21]Myint Z A W, Barry C. Iron and manganese dynamics in lake water [J].Water Research, 1999,33(8):157-164
[22]刘健康,高级水生生物学[M].北京：科学出版社.2002.1-197
[23]Dehning, I.& M. M. Tilzer,. Survival of Scenedesmus acuminatus in darkness. [J], Journal of Phycology,1989,25:509-515.
[24]Eiichi Furusato, Takashi Asaeda. Tolerance for prolonged darkness of three phytoplankt on species, Microsystems actions, Scenedesmus quadricauda, and Melosira ambigua,[J] Hydrobiologia,2004,527:153-162
[25]李杰,欧丹云,宋立荣.微囊藻衰亡过程研究-四种模拟胁迫条件下微囊藻的衰亡生理,[J]湖泊科学.2008,20(5)：549-555
[26]王福军.计算流体力学分析[M].北京：清华大学出版社,2006
[27]韩占忠,王敬,兰小平.FLUENT流体工程仿真计算实例与应用[M].北京：北京理工大学出版社,2006
[28]王瑞金,张凯,王刚．Fluent技术基础与应用实例[M].北京,清华大学出版社,2007
[29]薛胜伟,尹侠.气升式内环流反应器流场及传质性数值模拟[J].化学工程,2006,34(5)：23-2
[30]张善发,马鲁铭,高延耀,合流制溢流污水的一级化学强化处理,中国给水排水,2005,(11)
[31]肖尧,施汉昌,范笼,基于计算流体力学的辐流式二沉池数值模拟,中国给水排水,2006(19)
[32]曾光明,蒋益民等,平原区二维复杂河流水质模拟计算[J],环境科学学报,2005,5,18-22
[33]叶闽,陈惠敏,一维垂向水温分布模型在深水型水库中的应用[J].水系污染与保护,1999,1：34-38
[34]王煜,戴会超,大型水库水温分层影响及防治措施[J],三峡大学学报,2009,31(6)：11-14
[35]任华堂,陈永灿,刘邵炜.大型水库水温分层数值模拟[J].水动力学研究 与进展.2007,22(6)：667-675
[36]Gustavo C. Buscaglia, Fabian A. Bombardelli, Marcelo H. Garcia. Numerical modeling of large-scale bubble plumes accounting for mass transfer effects [J]. International Journal of Multiphase Flow,2002,28(11):1763-1785.
[37]张军,郑捷庆.气—幂律两相流体流经截面突缩管的数值模拟.石油钻采工艺,2007,29(3)：108-113
[38]王霞,金志浩.流体数值模拟中二维、三维模型结果比较研究.沈阳化工学院学报,2007,21(2)：121-123
[39]Fluent Inc., FLUENT User's Guide [M]. Fluent Inc.,2003
[40]Fluent Inc., FLUENT User Defined Function Manual [M]. Fluent Inc.,2003
[41]李西京,张瑞佟.水库水温分层模型及黑河水库水温预测[J].西北水电,1994,3：31-36
[42]樊尔兰,李怀恩.黑河分层型水库水量水质综合优化调度的研究[J].系统工程学报,1996,11(1)：63-70
[43]邓云,李嘉.河道型深水库的温度分层模拟[J]冰动力研究与进展,2004,19(5)：604-609
[2]朱智,吴江明,周俊杰.滇池污染治理工作若干问题的思考[J].中国给水排水,1999,15(12)：27-30
[3]黄廷林,丛海兵,柴蓓蓓.饮用水水源水质污染控制[M].北京.中国建筑工业出版社.2009：122
[4]Gary J. Jones, Wojciech Poplawski. Understanding and management of Cyanobacterial blooms in sub-tropical reservoirs of Queensland,[J].water science technology,1998,37(2): 161-168
[5]金相灿,荆一凤,刘文生.湖泊污染底泥疏浚技术[J].环境科学研究,1999,12(5)：9-12
[6]Friedrich Recknagel, Masaaki Hosomi, Takehiko Fukushima, et al. Short-and Long-term Control of External and Internal Phosphorus Loads in Lakes——a scenario analysis[J]. Water Research,1995,29(7):1767-1779
[7]Milan Straskraba. Ecotechnological Methods for Managing Non-point Source Pollution in Watersheds, Lakes and Reservoirs[J]. Wat. Sci.Tech,1996,33(4-5):73-80
[8]丛海兵,扬水曝气水源水质改善技术研究[D].西安：西安建筑科技大学,2007.
[9]刘建康,谢平.用鲢鳙直接控制微囊藻水华的围隔试验和湖泊实践[J].生态科学,2003,22(3)：193-196.
[10]罗阳,刘敬.控制湖泊内源磷负荷的有效性研究[J].水资源保护,1996,2：52-55
[11]Petra M.Visser,Henk A.M Ketelaars.Reduced growth of the cyanobacterium microcystis in an artificially mixed lake and reservioir[J].Water science technology,1995,32(4):53-54
[12]Holdren C, W Jones, J Taggart. Managing Lakes and Reservoirs[M].3rd edition Prep. By N. Am. Lake Manage. Soc. And Terrene Inst., in coop, with U. S. EPA.,2001
[13]Murphy T. P., Lawson A., Kumagai M. Review of emerging issue in sediment treatment [J]. Aquatic Ecosystem Health and Management,1999, (2):419-434
[14]Clasen J. Raw water quality management at Wahnbach reservoir [J]. Water supply,2000,18(1):581-585
[15]丛海兵,黄廷林,缪晶广等.水体修复装置——扬水曝气器的开发.[J]中国给水排水,2005, 21(3)：41-45
[16]丛海兵,黄廷林,缪晶广等.扬水曝气器的水质改善功能及提水、充氧性能研究.[J]环境工程学报,2007,1(1)：7-13
[17]丛海兵,黄廷林,赵建伟等.扬水曝气器技术在水源水质改善中的应用.[J]环境污染与防治,2006,28(3)：215-218
[18]朱伟峰,基于CFD的扬水曝气器外围流场及曝气室流场模拟.[D]西安,西安建筑科技大学,2008.
[19]黄廷林,李建军.扬水曝气技术对汾河水库原水水质的改善.[J],供水技术,2007,10：13-16
[20]李素琴.浅谈汾河水库水质的改善.[J],科技情报开发与经济,2007,17：251-252
[21]Myint Z A W, Barry C. Iron and manganese dynamics in lake water [J].Water Research, 1999,33(8):157-164
[22]刘健康,高级水生生物学[M].北京：科学出版社.2002.1-197
[23]Dehning, I.& M. M. Tilzer,. Survival of Scenedesmus acuminatus in darkness. [J], Journal of Phycology,1989,25:509-515.
[24]Eiichi Furusato, Takashi Asaeda. Tolerance for prolonged darkness of three phytoplankt on species, Microsystems actions, Scenedesmus quadricauda, and Melosira ambigua,[J] Hydrobiologia,2004,527:153-162
[25]李杰,欧丹云,宋立荣.微囊藻衰亡过程研究-四种模拟胁迫条件下微囊藻的衰亡生理,[J]湖泊科学.2008,20(5)：549-555
[26]王福军.计算流体力学分析[M].北京：清华大学出版社,2006
[27]韩占忠,王敬,兰小平.FLUENT流体工程仿真计算实例与应用[M].北京：北京理工大学出版社,2006
[28]王瑞金,张凯,王刚．Fluent技术基础与应用实例[M].北京,清华大学出版社,2007
[29]薛胜伟,尹侠.气升式内环流反应器流场及传质性数值模拟[J].化学工程,2006,34(5)：23-2
[30]张善发,马鲁铭,高延耀,合流制溢流污水的一级化学强化处理,中国给水排水,2005,(11)
[31]肖尧,施汉昌,范笼,基于计算流体力学的辐流式二沉池数值模拟,中国给水排水,2006(19)
[32]曾光明,蒋益民等,平原区二维复杂河流水质模拟计算[J],环境科学学报,2005,5,18-22
[33]叶闽,陈惠敏,一维垂向水温分布模型在深水型水库中的应用[J].水系污染与保护,1999,1：34-38
[34]王煜,戴会超,大型水库水温分层影响及防治措施[J],三峡大学学报,2009,31(6)：11-14
[35]任华堂,陈永灿,刘邵炜.大型水库水温分层数值模拟[J].水动力学研究 与进展.2007,22(6)：667-675
[36]Gustavo C. Buscaglia, Fabian A. Bombardelli, Marcelo H. Garcia. Numerical modeling of large-scale bubble plumes accounting for mass transfer effects [J]. International Journal of Multiphase Flow,2002,28(11):1763-1785.
[37]张军,郑捷庆.气—幂律两相流体流经截面突缩管的数值模拟.石油钻采工艺,2007,29(3)：108-113
[38]王霞,金志浩.流体数值模拟中二维、三维模型结果比较研究.沈阳化工学院学报,2007,21(2)：121-123
[39]Fluent Inc., FLUENT User's Guide [M]. Fluent Inc.,2003
[40]Fluent Inc., FLUENT User Defined Function Manual [M]. Fluent Inc.,2003
[41]李西京,张瑞佟.水库水温分层模型及黑河水库水温预测[J].西北水电,1994,3：31-36
[42]樊尔兰,李怀恩.黑河分层型水库水量水质综合优化调度的研究[J].系统工程学报,1996,11(1)：63-70
[43]邓云,李嘉.河道型深水库的温度分层模拟[J]冰动力研究与进展,2004,19(5)：604-609
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