ONE-AND TWO-DIMENSIONAL COUPLED HYDRODYNAMICS MODEL FOR DAM BREAK FLOW

1-D and 2-D mathematical models for dam break flow were established and verified with the measured data in laboratory. The 1-D and 2-D models were then coupled, and used to simulate the dam break flow from the reservoir tail to the dam site, the propagation of dam break waves in the downstream channel, and the submergence of dam break flow in the downstream town with the hydrodynamics method. As a numerical example, the presented model was employed to simulate dam break flow of a hydropower station under construction. In simulation, different dam-break durations, upstream flows and water levels in front of dam were considered, and these influencing factors of dam break flow were analyzed, which could be referenced in planning and designing hydropower stations.

Study of total variation diminishing (TVD) slope limiters in dam-break flow simulation

A two-dimensional （2D） dam-break flow numerical model was developed based on the finite-volume total variation diminishing （TVD） and monotone upstream-centered scheme for conservation laws （MUSCL）-Hancock scheme, which has second-order accuracy in both time and space. A Harten-Lax-van Leer-contact （HLLC） approximate Riemann solver was used to evaluate fluxes. The TVD MUSCL-Hancock numerical scheme utilizes slope limiters, such as the minmod, double minmod, superbee, van Albada, and van Leer limiters, to prevent spurious oscillations and maintain monotonicity near discontinuities. A comparative study of the impact of various slope limiters on the accuracy of the numerical flow model was conducted with several dam-break examples including wet and dry bed cases. The numerical results of the superbee and double minmod limiters agree better with the theoretical solution and have higher accuracy than other limiters in one-dimensional （1D） space. The ratio of the downstream water depth to the upstream water depth was used to select the proper slope limiter. For the 2D numerical model, the superbee limiter should not be used, owing to significant numerical dispersion.

基于CEL方法的带结构物溃坝流数值模拟

随着全球气温的不断升高,极端天气现象增多,溃坝现象成为水工结构方向需要重点防范的自然灾害。溃坝流的发展会对下游结构物产生巨大的破坏作用,因此深入探究溃坝流现象的水动力学特性以及溃坝流下游结构物所受到的冲击力影响势在必行。本文针对带有结构物的溃坝流动问题现象,采用CEL方法(Coupled Eulerian-Lagrangian analysis,耦合欧拉-拉格朗日方法),对于溃坝流的发展、演化进行了数值模拟。研究结果表明,模拟结果中溃坝流自由表面及流体尖端时程变化与文献试验结果拟合较好,CEL方法可应用在溃坝流现象的模拟,并且具有较好的准确性和精度。结构物材料性能、高度及与结构物与溃坝流间的位置,均会影响溃坝流的运动状态以及结构物的受力变形状态,在不考虑结构物破坏的情况下,提高结构物弹性模量,增加结构物高度,以及减小结构物与溃坝流间的距离均可提高结构物对于溃坝流的阻挡作用。

基于FLOW-3D的尾矿库逐渐溃坝三维数值模拟

为了分析尾矿库逐渐溃坝时溃口随时间的变化过程以及溃坝后尾砂的淹没范围,基于FLOW 3D软件建立了三维数值模型。模拟了水槽内的逐渐溃坝,将计算得出的溃口形态变化数据以及水位数据与实验数据进行对比,结果基本吻合,验证了数值模拟的精确性和可靠性。以某尾矿库为例,利用该数值模型模拟逐渐溃坝,结果表明:尾矿坝溃决时先冲刷溃口底部,而后逐渐向两侧侵蚀,坝体侵蚀断面呈U型分布,随着水量减少,泥沙慢慢沉积,最终稳定,泥沙下泄量约为总泥沙量的31.1%,随着距离的推移,泥沙淤积量沿程减少,下游房屋监测点最大水深15.44 m。

溃坝洪水演进一维水动力模型

中国是受洪水灾害影响最严重的国家之一。洪水数值模型可准确地反映洪水的演进与致灾过程。本研究针对天然河道洪水过程存在的尺度大、水流流态复杂、河道断面形式多变以及计算建模困难等问题,提出一套基于Godunov格式的有限体积法离散圣维南方程组的一维水动力模型,并采用求解复杂断面水力要素之间关系的方法,提高了一维水动力模型求解的精度与效率,精确地反映了复杂断面河道的水流运动特性。将模型模拟得到的数值解与算例中的解析解或实测数据进行对比,结果表明:(1)构建的一维水动力模型模拟结果与理想算例解析解及实验实测数据吻合程度均较高,所有算例的E NS均大于0.5,说明模型具有良好的稳定性和适应性;(2)将模型应用至金沙江白格堰塞湖溃坝洪水算例中,模拟得到的流量峰值及整体洪水过程均与实测过程吻合较好,在叶巴滩和苏洼龙两个测点处E NS分别为0.633和0.812,证明了模型在实际应用中的适用性与可靠性。结果表明,开发的一维水动力模型对溃坝洪水等水流流态复杂、突发性强的洪水过程具有良好的模拟效果。本研究可为河道及溃坝洪水风险的初步、快速评估等工作提供有效的模拟支撑。

上游水库溃坝对铁路货场的影响分析

新建咸宁货场综合物流基地工程选址于王家祠水库下游,一旦水库发生溃坝,将对铁路货场的运营安全构成极大威胁。铁路勘测阶段通过详细调查水库情况,结合铁路工程水文勘测设计规范,研究了上游水库对新建货场选址处流量的影响,为货场的选址和设计提供了重要参考,相关研究思路可为类似铁路工程的勘察设计提供借鉴。

MIKE软件技术在水库溃坝洪水数值模拟中的应用研究

当前,水库大坝受到超频率的洪水以及强震破坏,而容易导致溃决风险。针对水库大坝溃决相关问题,融合BREACH和MIKE21构建耦合模型,并用于溃坝洪水数值模拟试验。结果表明,7种方案最大下泄流量为方案1的18.39×10^(4) m^(3)/s;方案1洪峰向地点C汇入点的洪水最大流量比邢台坝址下降约44%。方案1的溃坝洪水水位始终最高,A地最高为306m。综合来看,耦合模型在水库溃坝洪水数值模拟中具备有效性,在实际的水库防洪避险中具备实用性。

室内水槽溃坝模型试验及FLOW-3D模拟分析

为研究尾矿坝坝体稳定性对下游的影响,根据不同干密度的尾砂设置了室内水槽溃坝模型试验,并采用FLOW-3D软件,建立了三维模型进行模拟,比较了两者结果的吻合度,研究成果对矿坝选址与灾害预防有重要意义。

基于FLOW-3D的尾矿库数值模拟对下游影响研究

为研究尾矿库溃坝后对下游村庄的影响,通过对比采取工程措施前后监测点水位及通过断面的流量流速变化,分析采取工程措施的有效性及必要性.本文以某实际尾矿库为例,通过FLOW-3D软件进行三维数值模拟,建立了尾矿库及其下游3km范围内的实体地形及房屋和村庄三维数值模型,对尾矿库逐渐溃坝的动态过程进行了模拟计算;并在原尾矿库模型的基础上,在坝脚处增加一拦河坝,对比分析溃坝对下游的影响.结果显示:采取工程措施后,监测点水位明显降低,断面流量流速均有所减缓,并且推迟了出现最大流量流速的断面时间,证明采取工程措施是有效的.

黄土高原淤地坝溃损条件下坝地侵蚀机理及溃口水流特征

研究淤地坝溃损条件下的坝地侵蚀机理及水沙过程对于淤地坝的建设和后期管护具有重大意义。基于文献调研和实地调查分析,发现淤地坝溃损后的坝地侵蚀主要受坝地土体性质、坝地形成特征及淤地坝溃损模式影响,坝地侵蚀造沟模式可概括为“淤地坝溃损→溯源侵蚀→冲刷下切→沟壁坍塌→水沙混合流”;以山西省吕梁市离石区马槽里#2骨干坝为例,通过数值计算不同淤地工况下淤地坝溃损时的溃口流量过程和水位过程得知,淤地坝溃损条件下的水沙过程受库区的淤地情况显著变化,且坝地具有削峰落沙的作用。

Numerical and experimental investigation of three-dimensionality in the dam-break flow against a vertical wall

The three-dimensionality extent of the dam break flow over a vertical wall is investigated numerically and experimentally in this paper. The numerical method is based on Reynolds averaged Navier-Stokes（RANS） equation that describes the three-dimensional incompressible turbulent flow. The free surface is captured by using the unstructured multi-dimensional interface capturing（UMTHINC） scheme. The equations are discretized on 2-D and 3-D unstructured grids using finite volume method. The numerical simulations are compared with newly conducted experiment with emphasis on the effect of three-dimensionality on both free surface and impact pressure. The comparison between the numerical and experimental results shows good agreement. Furthermore, the results also show that 3-D motion of the flow originates at the moment of impact at the lower corners of the impact wall and propagates to the inner region as time advances. The origin of the three-dimensionality is found to be the turbulence development as well as the relative velocity between the side wall region and the inner region of the wave front at the moment of impact.

黄河下游透水丁坝瞬溃后水力及冲淤特性研究

溃坝是一种瞬时带有巨大破坏作用的灾害性过程,可引起河床的骤冲、骤淤以及下游岸滩失稳坍塌。基于MIKE21 FM软件构建二维水动力数值模型,模拟了黄河下游老君堂河段拟建透水丁坝群中首排丁坝瞬时全溃后所诱发的水流泥沙运动过程,分析了溃坝后床面剪切力的分布变化,阐明了坝群附近河床的冲淤特点。研究表明:首排坝瞬溃后,溃坝波受下游丁坝群的影响而改变了其传播演进过程线;溃坝对主槽的输沙能力影响较弱,但却显著地影响了坝区泥沙的起动和沉降;首排坝的坝体和次排坝的坝头是受损最严重的区域,因此建议采用实体丁坝与透水丁坝相结合的复合式配置方式,即首排坝和次排坝采用实体丁坝、其余位置采用透水丁坝,以加强各工况丁坝群运行的稳定性。

尾矿库溃坝对下游高速公路桥梁的损伤和滑动破坏评估

溃坝尾砂泥石流是介于水和一般自然界泥石流二者之间的一种颗粒相对均匀的砂—水混合物浆体,具有高势能、流速快的特性,易对下游高速公路造成巨大威胁,因此开展溃坝尾砂泥石流对下游高速公路的损伤评估,对于保障尾矿库下游高速公路安全具有重要意义。本研究基于尾矿库溃坝数值模拟并结合泥石流领域的损伤和滑动破坏研究,建立了溃坝尾砂泥石流对下游高速公路桥梁的损伤和滑动破坏评估模型。首先,进行尾矿库溃坝数值模拟确定高速公路桥墩前溃坝尾砂泥石流的流速和深度变化;然后,将流速和深度数值模拟结果代入计算公式对高速公路损伤和滑动破坏进行定量评估;最后得出评估结果。以铜山口尾矿库为例开展工程应用,研究结果表明:尾矿库溃坝后高速公路桥墩损伤满足要求,桥墩基础损伤评估中计算出局部冲刷最大深度为4.456 m,大于桥墩基础顶部距离地面的高度4 m,一部分桥墩基础将受到侵蚀破坏;桥梁滑动破坏评估中计算出桥墩抗滑动稳定性系数为1.02,低于规范限制1.2,高速公路桥梁存在横向滑动风险。

基于双向流固耦合模型的溃坝水流数值模拟

弹性结构在运动流体的作用下会产生动力响应,对结构本身的安全性和耐久性都提出了更高的要求。使用开源计算流体力学软件OpenFOAM和开源计算固体力学软件CalculiX建立双向流固耦合模型,对溃坝水流冲击刚性结构和弹性结构的过程进行了数值模拟。首先对比了代数流体体积法和几何流体体积法在分析溃坝水流冲击刚性结构时的精度,结果表明几何流体体积法能够更为准确地模拟剧烈变化的自由液面。进一步采用几何流体体积法对溃坝水流冲击弹性结构的双向耦合问题进行了分析,弹性结构的动力响应和自由液面的分析结果与前人的数值结果吻合良好,表明目前的数值模型可以应用到实际工程的流固耦合分析中。

基于生态系统服务价值的尾矿库溃坝短期生态环境损失评估

尾矿库溃坝不但会对下游居民生命财产安全构成威胁,而且会导致当地生态环境遭到严重破坏。为了定量评估尾矿库溃坝造成的生态环境损失,在溃坝尾砂流演进过程模拟的基础上,提出了基于生态系统服务价值的尾矿库溃坝生态环境损失评估方法。以江西省某铁矿尾矿库工程为例,模拟了溃坝尾砂流演进过程,获取了该尾矿库下游受灾区域分布及危险程度区划图,并从生态系统服务价值的角度评估了尾矿库溃坝造成的短期生态环境损失。结果表明:采用Bingham流变模型可有效模拟尾矿库溃坝及尾砂演进过程,获得尾矿库下游地区受灾情况;尾矿库下游地区受到溃坝影响的生态系统主要包括森林生态系统和农田生态系统,其中森林生态系统遭受的损失最大。所提方法可为类似尾矿库工程漫顶溃坝生态环境损失评估提供理论参考。

基于B样条物质点法的溃坝流模拟研究

溃坝流是水利工程中常见的一种自由表面流动问题,准确模拟溃坝流问题具有重要的工程意义.B样条物质点法(BSMPM)作为一种物质点法(material point method, MPM)的改进算法,其提高了物质点的计算精度和收敛性,且在自由表面流动问题中有独特的算法优势.基于B样条物质点法,通过引入人工状态方程,发展了一种弱可压缩B样条物质点法(WC-BSMPM);开展溃坝流问题的模拟研究,分析B样条插值基函数阶数对模拟结果的影响.结果表明:模拟所得流体波前位置、波前流速及给定位置处的高程变化与已有实验结果吻合较好;同时,随着B样条基函数阶数的增加,模拟结果与试验结果吻合度逐渐提高.随着基函数阶数的增加,计算耗时呈约1.5倍增长;不同阶次B样条物质点法的计算耗时随背景网格尺寸的增长率基本一致,约呈线性增长.验证了弱可压缩B样条物质点法模拟溃坝流问题的有效性,为模拟溃坝流问题提供了一种新的思路和方法.

真实地形下尾矿库溃坝尾砂流下泄过程数值模拟

为了研究尾矿库溃坝尾砂流对下游敏感目标的影响,以江西省某尾矿库为研究对象,建立了真实三维地形数值模型,利用FLOW-3D三维流体力学软件模拟分析了该尾矿库分别在不同工况下溃坝下泄尾砂流在下游1 km范围内的输移时空变化特征。结果表明:溃坝尾砂流的发展方向、分布情况、水深以及泥沙淤积受真实三维地形变化影响较为明显,溃坝尾砂流主要分布于下游稻田和低洼地段,浅溪河作为主要行洪通道,水深变化和泥沙淤积情况较为明显,只有已搬离的浅溪村受到尾砂流淹没,洪水最远到达港口村西部鱼塘,其余村庄均未受到影响。所得结果可以为尾矿库安全运行管理和制定溃坝应急预案提供依据。

EXPERIMENTAL STUDY OF DAM-BREAK FLOW IN CASCADE RESERVOIRS WITH STEEP BOTTOM SLOPE

Dam break can cause a significant disaster in the downstream, especially, in a valley with cascade reservoirs, which would aggravate the disaster extent. The experimental studies of the dam-break flow of cascade reservoirs are few and far between at the present, Most of related studies concern the failure of a single dam.. This article presents an experimental study of the characteristics of an instantly filled dam-break flow of cascade reservoirs in a rectangular glass flume with a steep bottom slope. A new method was used to simulate the sudden collapse of the dam. A series of sensors for automatic water-levels were deployed to record the rapid water depth fluctuation. The experimental results show that, the ratio of the initial water depth of the downstream reservoir to that of the upstream reservoir would greatly affect the flood peak water depth in the downstream reservoir area and in the stream channel behind the downstream dam, while the influence of the dam spacing is insignificant. In addition, the comparison between the single reservoir and the cascade reservoirs shows some difference in the dam-break flow pattern and the stage hydrograph at the corresponding gauging points.

FINITE-VOLUME TVD ALGORITHM FOR DAM-BREAK FLOWS IN OPEN CHANNELS

A finite-volume Total Variation Diminishing (TVD) scheme is presented formodeling dam-break flows in open channels. This method is used for solving the 2D shallow waterequations on arbitrary quadrilateral meshes, based upon a second-order hybrid TVD scheme with anoptimum-selected limiter in the space discretization and a two-step Runge-Kutta approach in the timediscretization. Verification for a circular dam-break problem is carried out by comparing thepresent results with others and very good agreement is shown. The present algorithm is then used topredict dam-break flow characteristics in open channels such as in furcated channels. Morecomplicated unsteady flow characteristics in these furcated channels than in the regular channelsstudied previously can observed in this work.

NUMERICAL SIMULATION OF TWO-DIMENSIONAL DAM-BREAK FLOWS IN CURVED CHANNELS

Two-dimensional transient dam-break flows in a river with bends were theoretically studied. The river was modeled as a curved channel with a constant width and a flat bottom. The water was assumed to be an incompressible and homogeneous fluid. A channel-fitted orthogonal curvilinear coordinate system was established and the corresponding two-dimensional shallow-water equations were derived for this system. The governing equations with well-posed initial and boundary conditions were numerically solved in a rectangular domain by use of the Godunov-type finite-difference scheme, which can capture the hydraulic jump of dam-break flows. The comparison between the obtained numerical results and the experimental data of Miller and Chaudry in a semicircle channel shows the validity of the present numerical scheme. The mathematical model and the numerical method were applied to the dam-break flows in channels with various curvatures. Based on the numerical results, the influence of river curvatures on the dam-break flows was analyzed in details.