两相流分离鳃的水沙流场数值模拟
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摘要
“垂向异重流式混合流体分离鳃”(简称分离鳃)是一种清洁、高效、成本低的水沙分离装置。前期的研究是基于大量的假设,通过试验来改变分离鳃的几何参数和水力参数,优化分离鳃的结构,这种研究方法的局限性越来越明显。
为了克服以往传统试验的局限性,本文应用数值方法模拟了分离鳃内固液两相流场,即应用大型流体软件FLUENT对分离鳃进行三维流场数值模拟,主要得到以下结论：
(1)分离鳃内存在两种流动的异重流现象：水沙绕鳃片形成的横向异重流、水沙绕容器边璧的垂向异重流及相邻鳃片之间的环流。鳃片上下各存在一个顺时针涡旋,两侧通道与鳃片上、下表面流速较大,其余区域流速很小
(2)分离鳃的浓度分布：鳃片上表面浓度较大,主要为泥沙,下表面浓度较小,为清水。在沉降过程中,浓度出现梯度变化,即：上层浓度逐渐减小,下层浓度逐渐增加。待沉淀结束后,分离鳃内浓度呈层分布,由上到下逐渐增大,存在四区两界面：清水区、絮凝区、成层沉淀区和泥沙压缩区,水沙分界面和压缩界面。
(3)对于没有进出流的分离鳃的数值模拟,层流模型的速度场和浓度场更接近实际,更适用于分离鳃的流场数值模拟。
(4)比较了单鳃片与多鳃片分离鳃装置的三维数值模拟结果,得到以下结论：多鳃片比单鳃片分离鳃有明显的优势,鳃片数目的增加,可以增加沉降速度,提高分离效率,为沉降创造有利条件。
(5)本文采用的数学模型是正确的,采用的数值计算方法是可靠的。
(6)推导了鳃片上的流速方程,并验证了内部水流稳定性。
The vertical-component density mixture flow separation device (VCDM) is a clean, efficient and low cost of water and sediment separation device.Based on a lot of assumptions, Preliminary research had Optimized the structure of VCDM through changed Geometric and operating parameters in experiments.The limitation of this conventional method is more and more evident
In order to overcome the limitations of the preliminary research, the author simulated in VCDM solid-liquid two-phase flow using a numerical method (FLUENT). The main conclusions are as follows:
(1) There have three exists two density flow that Water and sediment around the gills slice and containers edge of debir filed between two gills slice and in VCDM. Gills slice up and down have clockwise whirlpools each other. The velocity is larger in the side channels and gills slice fluctuation surface,but the rest area is very small.
(2) Concentration distribution in VCDM:The concentration of the gills slice upper surface is bigger,mainly for sediment;the concentration of the gills slice nether surface is lower,mainly for water. In the settlement process,concentration gradient change:the upper concentration gradually decrease, the bottom concentration gradually increase. When precipitation ended,concentration gradually increase from top to bottom in VCDM. There are four district and two interface:water area, flocculation area, into layer precipitation area and sedimentation compression area; water and sediment boundary surface and compression interface.
(3) Without access flow of VCDM, the laminar model's velocity field and concentration field more similar to the actual flow field.So the laminar model more suitable for the flow numerical simulation.
(4) Compared with the single gills slice and five gills slice, get the following conclusion:Five gills slice have obvious advantage. Increase the number of the gills slice can the subsiding speed, improve the separation efficiency, to create favorable conditions for settlement.
(5) Using mathematical model is correct and the numerical calculation method is reliable.
(6) The author deduced the velocity equation on the gills slices, and verified internal flow stability.
为了克服以往传统试验的局限性,本文应用数值方法模拟了分离鳃内固液两相流场,即应用大型流体软件FLUENT对分离鳃进行三维流场数值模拟,主要得到以下结论：
(1)分离鳃内存在两种流动的异重流现象：水沙绕鳃片形成的横向异重流、水沙绕容器边璧的垂向异重流及相邻鳃片之间的环流。鳃片上下各存在一个顺时针涡旋,两侧通道与鳃片上、下表面流速较大,其余区域流速很小
(2)分离鳃的浓度分布：鳃片上表面浓度较大,主要为泥沙,下表面浓度较小,为清水。在沉降过程中,浓度出现梯度变化,即：上层浓度逐渐减小,下层浓度逐渐增加。待沉淀结束后,分离鳃内浓度呈层分布,由上到下逐渐增大,存在四区两界面：清水区、絮凝区、成层沉淀区和泥沙压缩区,水沙分界面和压缩界面。
(3)对于没有进出流的分离鳃的数值模拟,层流模型的速度场和浓度场更接近实际,更适用于分离鳃的流场数值模拟。
(4)比较了单鳃片与多鳃片分离鳃装置的三维数值模拟结果,得到以下结论：多鳃片比单鳃片分离鳃有明显的优势,鳃片数目的增加,可以增加沉降速度,提高分离效率,为沉降创造有利条件。
(5)本文采用的数学模型是正确的,采用的数值计算方法是可靠的。
(6)推导了鳃片上的流速方程,并验证了内部水流稳定性。
The vertical-component density mixture flow separation device (VCDM) is a clean, efficient and low cost of water and sediment separation device.Based on a lot of assumptions, Preliminary research had Optimized the structure of VCDM through changed Geometric and operating parameters in experiments.The limitation of this conventional method is more and more evident
In order to overcome the limitations of the preliminary research, the author simulated in VCDM solid-liquid two-phase flow using a numerical method (FLUENT). The main conclusions are as follows:
(1) There have three exists two density flow that Water and sediment around the gills slice and containers edge of debir filed between two gills slice and in VCDM. Gills slice up and down have clockwise whirlpools each other. The velocity is larger in the side channels and gills slice fluctuation surface,but the rest area is very small.
(2) Concentration distribution in VCDM:The concentration of the gills slice upper surface is bigger,mainly for sediment;the concentration of the gills slice nether surface is lower,mainly for water. In the settlement process,concentration gradient change:the upper concentration gradually decrease, the bottom concentration gradually increase. When precipitation ended,concentration gradually increase from top to bottom in VCDM. There are four district and two interface:water area, flocculation area, into layer precipitation area and sedimentation compression area; water and sediment boundary surface and compression interface.
(3) Without access flow of VCDM, the laminar model's velocity field and concentration field more similar to the actual flow field.So the laminar model more suitable for the flow numerical simulation.
(4) Compared with the single gills slice and five gills slice, get the following conclusion:Five gills slice have obvious advantage. Increase the number of the gills slice can the subsiding speed, improve the separation efficiency, to create favorable conditions for settlement.
(5) Using mathematical model is correct and the numerical calculation method is reliable.
(6) The author deduced the velocity equation on the gills slices, and verified internal flow stability.
引文
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[4]和彦杰.斜板沉降器固液两相流数值模拟及分离性能研究[D].四川：四川大学,2001：1-2.
[5]郭生昌.沉淀池的计算机数值模拟[D].上海：东华大学,2004：1-2.
[6]王福军.计算流体动力学分析—CFD软件原理与应用[M].清华大学出版社,2004：1-4.
[7]George Tchobanoglous, Franklin L.Burton, H. David Stensel. Waste water Engineering:Treatment and Reuse (Fourth Edition).2002. Metealf & Eddy, Ine.:361-415.
[8]Camp T. R Sedimentation and the Design of settling Tnaks[J], Transaction ASCE,1946, (3):895-936.
[9]Schamber D. R, Larock B. E Numerical analysis of flow in sedimentationBasins[J]. Journal of Hydarulic Division ASCE,1981,107(5):575-591.
[10]Lansen P. On the hydraulics of rectangular settling basins, experimental and theoroetical studies. Report no.1001, Dept. of Engineenng Lund Inst. of Teeh. Lund Univ, Lund, Sweden,1977.
[11]Imam E, McCorquodale J A, Bewtra J K. Numetcal modelling of sedimentation tanks. Journal of Hydraulic Engineering,1983,109(12):1740-1754.
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[14]I. Takacs, G. G.Patry, D. Nolasco. A Dynamic Model of the Clarification-Thickening Process. Wat. Res.1991,25(10):1263-1271.
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[16]J. A. Mc Corquodale, S. Zhou. Effects of Hydraulic and Solids Loading on Clarifier Performance.J. Hydraul. Res.1993,31(4):461-477.
[17]张庄.沉沙池沉淀效果的数值分析[J].清华大学学报(自然科学版),1998,38(1)：96-99.
[18]蔡金傍,朱亮,段祥宝,等.平流沉淀池数值模拟分析[J].河海大学学报,2004,32(1)：27-31.
[19]何国建.沉淀池的重要结构参数研究[D].南京：河海大学,2004.
[20]屈强,马鲁铭,王红武.辐流式二沉池固液两相流数值模拟[J].同济大学学报(自然科学版),2006,34(9)：1212-1216.
[21]王晓玲,杨丽丽,张明星,等.平流式沉淀池水流三维CFD模拟[J].天津大学学报,2007,40(8)：921-930.
[22]蒋成义,吴春笃,黄卫东,等.辅流式二沉池中异重流的计算流体力学模型研究[J].水科学进展,2007,18(6)：846-852.
[23]刘百仓,罗麟,马军,等.圆形沉淀池内温差异重流与浮力流的数值模拟[J].四川大学学报,2009,41(1)：34-40.
[24]李琳,邱秀云.浑水水力分离装置中水沙两相湍流的数值模拟[J].水利学报,2007,38(11)：1279-1284.
[25]李琳,邱秀云,龚守远,等.浑水水力分离清水装置内弱旋流场数值模拟[J].水力发电学报,2008,2(12)：67-71.
[26]李琳,邱秀云.浑水水力分离清水装置内水沙两相弱旋流场数值模拟[J].中国农村水利水电,2008(1)：11-19.
[27]邱秀云,龚守远,严跃成,等.一种新型水沙分离装置的研究[J].新疆农业大学学报,2007,30(1)：68-70.
[28]朱超,邱秀云,刘艳.垂向异重流式水沙分离鳃鳃片型式对水沙分离的影响研究[J].新疆农业大学学报,2008,31(6)：72-75.
[29]朱超,邱秀云.垂向异重流式分离鳃适用泥沙的试验研究[J].人民长江,2009,40(5)：60-61.
[30]朱超,邱秀云,孙鑫.垂向异重流式分离鳃鳃片倾角对水沙分离影响的试验研究[J].人民黄河,2009,31(7)：86-87.
[31]朱超,邱秀云.垂向异重流式水沙分离鳃水沙分离机理浅析[J].水利水电科技进展,2009,29(5)：20-23.
[32]朱超.水沙分离鳃结构优化及分离机理试验研究[D].新疆：新疆农业大学,2008,24(2)：42-45.
[33]张翔,邱秀云,李琳.垂向异重流式分离鳃在动水中的集成试验研究[J].新疆农业大学学报,2010.33(4)：1-4.
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