用三维VOF模型对横置圆筒绕流流场的数值模拟

以物理模型试验为基础,利用VOF模型与RNGkε湍流模型相结合的方法,对横置圆筒绕流流场进行三维数值模拟。通过建立模型,分析不同时刻计算域内的相体积分布及其圆筒周围速度场和压力场的分布,并将数值模拟结果与物理模型试验结果进行对比,结果表明,模拟值与试验值吻合较好,且其结果符合流体动力学基本理论,并说明VOF能够有效模拟水流自由表面,适用于闸门等水工建筑物内水流流动的数值模拟。     

基于VOF模型的团山子溢流坝数值模拟

本文介绍了VOF 模型,结合k-ε紊流模型,利用Fluent软件数值求解了带自由水面的二维水流流动问题。以团山子水利枢纽为例,计算了溢流坝内水流流动特性,并将计算结果与实验数据进行对比,结果表明计算值与实测值吻合较好,说明VOF 模型能够精确地跟踪自由表面,可利用数值模拟对泄水建筑物设计方案比选,结合模型试验的方法,研究其水力特性。     

多弯道溢洪道水力特性数值模拟研究

文中在物理模型试验的基础上,对多弯道溢洪道进行了数值模拟研究。采用FLUENT软件,引入适用于分层两相流的流体体积分数(VOF)模型求解自由水面曲线,成功地对龙屯水库多弯道溢洪道进行了三维紊流数值模拟,得到了自由水面、溢洪道底板压力、断面流速大小和三维流场的分布规律,并将数值模拟结果与试验结果进行了分析对比,两者基本吻合。试验结果表明:合理的选择数值模拟模型及参数,可以很好地模拟水流流态,可为工程所用。     

三维数值模拟分析在马岩洞水电站大坝表孔泄流设计中的运用

本文采用k-ε紊流数学模型,用VOF方法来模拟跟踪自由水面,求解三维数值方程,对不同体形情况下大坝表孔的泄水建筑物水流流动进行了数值计算,得出水流流动的参数,并计算出了挑射水流形态.通过比较分析,优化了泄水建筑物体形,为工程设计提供参考.     

多孔溢洪道泄流三维数值模拟

为了充分体现闸墩对过坝水流的影响，采用有限体积法对含多个孔和多个闸墩的溢洪道进行了水流的三维数值模拟，采用k-ε紊流模型，利用VOF方法处理自由水面，给出了泄流能力、水面线和压力分布。数值模拟结果与模型试验结果对比表明，使用的模型能精确的模拟溢洪道的过坝水流。计算发现，溢洪道不同孔由于受闸墩、边墩等的影响，过坝水流的水面线、坝面压力有着一定的差异，从而为溢洪道的水力设计提供可靠的设计依据。     

溃坝水流在复杂河道中传播的三维数值模拟

为研究河道弯曲和障碍物对溃坝波传播的影响,采用有限体积法对描述水流运动紊流模型和描述自由水面运动的VOF方程进行离散,建立了溃坝水流运动的三维数学模型,并对急弯河道进行了数值模拟计算。急弯河道溃坝波传播过程的模拟结果与前人实体模型试验结果基本一致。利用该模型研究了丁坝附近溃坝波传播的特性和溃坝水流的内部结构,数值模拟结果表明,溃坝波的传播受河道弯曲或障碍物的影响,产生反射和绕射,使得局部溃坝水流呈明显的三维特性。上游丁坝迎水面受到溃坝波波前的直接冲击,其动水压力远大于作用于下游丁坝的动水压力。另外,障碍物对溃坝水流的影响主要局限在障碍物上游和下游一定范围内,在此范围外,水流呈二维或一维特性。     

水闸消能防冲的数值模拟

本文结合长兴岛创建水闸工程设计实例,采用K-ε紊流模型和体积率（VOF）跟踪自由水面的方法,模拟了闸后消能防冲水流结构。将消能防冲的数值模拟结果,包括自由表面位置和水跃长度,与工程设计计算进行了对比分析。验证了工程设计的合理性和科学性。     

汤河水库弯曲溢洪道流场数值模拟分析

依据RNGk-ε双方程紊流模型,并采用VOF方法追踪自由水面和笛卡尔网格法处理复杂几何边界,对汤河水库溢洪道弯道水流进行了三维数值模拟,得到不同流量下溢洪道弯道的自由水面线、压力分布以及流速等流场参数分布规律。     

水平向涡流水流结构与气体迁移扩散特性研究

在掺气减蚀研究中,气体的迁移扩散对减蚀效果有重要影响.为研究水平向涡流水流中的气体迁移扩散特性,建立了水平向涡流模型,通过物理模型试验及数值模拟对水平向涡流掺气水流进行分析.结果表明:数值模拟计算能较为全面地提供三维流动的流场分布情况;水流结构可划分为附壁流动区、水平向涡流区、壅水回流区以及表面旋滚区;气体卷吸的部位是...     

小半径大底坡溢洪道弯道水流三维流场数值计算分析

水利枢纽溢洪道设计过程中常遇到陡槽弯道水流问题,复杂的弯道水流流态直接影响建筑物的布置和运行安全,对溢洪道陡槽弯道水力特性的研究具有现实和理论意义.本文采用RNGk-ε双方程模型模拟紊流,流体体积分数法(VOF)追踪自由水面,笛卡尔自适应网格与部分面积体积障碍模拟法(FAVOR)处理复杂的几何边界,成功地对小半径、大底坡溢洪道陡槽弯道流场进行了三维紊流数值模拟,得到了自由水面、断面流速大小、分布和三维流场的分布规律,结果分析表明数值模拟与物理实验结果两者吻合较好.     

浓度及温度场问题三维数值模拟及应用

研究温度和污染物的扩散规律,对于健康河流具有十分重要的意义。在排水口附近,温度和污染物的扩散具有很强的三维性。在已开发的三维紊流水动力模型基础上,研制了浓度及温度场三维数学模型。在模型中,空度用来处理不规则边界,VOF用来处理自由面。另外,模型还采用了k-ε紊流模型和壁面函数。利用建立的模型,对水槽和天然的排水口附近的水位、流场、紊动能及其扩散率、温度场和浓度场的分布规律等进行了模拟和研究。通过研究进一步认识了排水口局部三维水流运动规律,浓度和温度扩散规律及分布。     

3-D TURBULENT FLOW SIMULATION FOR THE TAIL WATER CHANNEL

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3D CFD validation of invert trap efficiency for sewer solid management using VOF model

Earlier investigators have numerically carried out performance analysis of the invert trap fitted in an open channel using the stochastic discrete phase model(DPM) by assuming the open channel flow to be closed conduit flow under pressure and assuming zero shear stress at the top wall.This is known as the fixed lid model.By assuming the top wall to be a shear free wall,they have been able to show that the velocity distribution looks similar to that of an open channel flow with zero velocity at the bottom and maximum velocity at the top,representing the free water surface,but no information has been provided for the pressure at the free water surface.Because of this assumption,the validation of the model in predicting the trap efficiency has performed significantly poorly.In addition,the free water surface subject to zero gauge pressure cannot be modeled using the fixed lid model because there is no provision of extra space in the form of air space for the fluctuating part of the water surface profile.It can.however,be modeled using the volume of fluid(VOF) model because the VOF model is the appropriate model for open channel or free surface flow.Therefore,in the present study,three-dimensional(3D) computational fluid dynamics(CFD) modeling with the VOF model,which considers open channel flow with a free water surface,along with the stochastic DPM.was used to model the trap efficiency of an invert trap fitted in an open rectangular channel.The governing mathematical flow equations of the VOF model were solved using the ANSYS Fluent 14.0 software,reproducing the experimental conditions exactly.The results show that the 3D CFD predictions using the VOF model closely fit the experimental data for glass bead particles.     

气液两相流理论在明渠水气界面计算中的应用

采用一维水面线计算方法确定断面和比降频繁变化、同时受下游回水影响的渠道水气界面位置往往产生较大误差。本文采用了两相流理论中三维相间界面计算模型－VOF模型模拟计算断面和比降频繁变化，受下游回水影响严重的渠道水气界面。实例资料的验证表明，VOF模型可以完全考虑渠道在三维空间上的变化以及下游回水的影响，是一种比一维渐变流水面线计算方法更为精细的数值模型。     

台阶坝面消能水气两相流数值模拟

 采用VOF法模拟自由表面,用非结构网格来处理复杂的边界形状,并根据边界形式进行适当的分区,利用k-ε气液两相流模拟光面和台阶溢流面的流场,得到了溢流面的流场、水面线以及消能率等相关水力参数。数值模拟试验结果表明,台阶溢流坝面水流紊动掺气充分,消能率较高,并与物理模型试验结果进行对比分析,二者吻合良好。     

典型非稳态水跃现象的数值研究

采用VOF模型跟踪自由表面的变化,数值模拟了典型水跃湍流由静止到最终稳定的全过程。本文给出了水跃现象在不同时刻自由表面的变化情况,主要对水跃过程中自由表面的形状、内部流场结构、速度矢量场及压力场分布进行了分析。结果表明,VOF模型能够有效地描述水跃这类复杂自由表面流道的湍流特性,具有可行性与实用性。     

A CFD Modeling Approach for Municipal Sewer System Design Optimization to Minimize Emissions into Receiving Water Body

The design of the urban sewage system is site specific, and it makes the use of three-dimensional (3D) model an alternative to a field study or a laboratory experiment. However, the use of 3D computational fluid dynamics (CFD) in the study of the urban sewage system has been generally limited to the study of a single structural component with simplified assumptions. In this study, the 3D model that adopted the renormalized group (RNG) k-ε turbulence model, the volume of fluid (VOF) free water surface model and the particle tracking approach was verified comparing the predicted flow field data with the measurements in laboratory scale experiments. Then, the model was applied to optimize the design of the combined sewer system (CSS) in the city of Edmonton with multiple hydraulic structures. Considering the details of predicted flow characteristics and the behaviors of the suspended solids, the final design was chosen and implemented to reduce the water pollution induced by the direct combined sewer overflow (CSO) discharge to the receiving water body. It is shown that the proposed 3D CFD modeling approach is a cost-effective tool to design the municipal sewer system.     

APPLICATION OF VOF TECHNIQUE TO CHANNEL IMPROVEMENT FOR PANJIATAI SHOAL IN THE YELLOW RIVER

In this paper, Volume Of Fluid (VOF) technique is used to simulate the free surface and the flow field affected by the groynes in the experimental flume and the natural river. A series of flume experiments are carried out. According to the orientation of groynes, angles from the flow direction to the axis of the groyne used in the experiments are assorted into obtuse angle, right angle, and acute angle as well. For each arrangement option, flow conditions are classified as the submerged and the non submerged one. Velocities and the water level affected by single groyne or double-groyne are measured. The calculated results are agreement well with the experimental data. Because of the high demands in the mesh quality and the computer capability, the VOF technique is seldom used to simulate the natural river. In this paper, the VOF technique is also used to simulate the Panjiatai Shoal of 2km long, one of the important improvement reaches in the Yellow River. Two improvement schemes are compared and analyzed, and the better one is recommended.     

NUMERICAL INVESTIGATION OF FLOW OVER A WEIR

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三维宽顶堰紊流场数值模拟及分析

本文利用三雏标准k-ε紊流数学模型,选择VOF方法追踪自由表面,采用气液两相流计算模型对宽顶堰流场进行了数值模拟,计算结果与试验数据较为吻合.模拟结果表明,数值模拟能够广泛应用于数值模拟带有复杂自由表面的泄水建筑物紊流场.