Numerical Simulation of Dam Breaking Using Smoothed Particle Hydrodynamics and Viscosity Behavior

Smoothed particle hydrodynamics (SPH) is a Lagrangian meshless particle method. It is one of the best method for simulating violent free surface flows in fluids and solving large fluid deformations. Dam breaking is a typical example of these problems. The basis of SPH was reviewed, including some techniques for governing equation resolution, such as the stepping method and the boundary handling method. Then numerical results of a dam breaking simulation were discussed, and the benefits of concepts like artificial viscosity and position correction were analyzed in detail. When compared with dam breaking simulated by the volume of fluid (VOF) method, the wave profile generated by SPH had good agreement, but the pressure had only reasonable agreement. Improving pressure results is clearly an important next step for research.

Analysis of the wave propagation and the flow char-acteristics around cylinder due to dam break water

Dam breaks are easily triggered by heavy rains due to extreme weather such as typhoons,causing serious economic losses and casualties.Through the investigation of Chaoshan coastal zone,it is found that there have been dam breaks caused by geological disasters.In the design and management of water conservancy project,it is very important to analyze the effect of disastrous flow caused by dam break on the building.In this paper,the effect of the dam break flow on the cylinder is simulated numerically by taking the water body with initial velocity as the dam break flow,and the flow characteristics around the cylinder and the water body are analyzed.Numerical model adopted the Renault Average Navier-Stokes(RANS)model and volume of fluid(VOF)method to analyze the evolution of free water surface.It is found that there are different patterns of water movement in the process of dam break resulting in the creation of several isolated convex hull forms of dam-break waves on the stationary water surface,which causes longer disturbances in the water near the cylinder and makes the cylinder more vulnerable to fatigue damage.The increase of the height of the dam breaking water will lead to the increase of the hydrodynamic force on the pipeline.This study has guiding significance for the study of dam break and dam body design in water conservancy projects.

Mitigation of the amplitude and celerity of dam break shock wave using combination of groyne and vertical pier

This paper aims to numerically investigate the impact of the combination of groynes and vertical piers on mitigating the amplitude and celerity of dam break wave-front.First,a robust numerical model based on the Finite Volume Method(FVM)with the Harten,Lax and van Leer(HLL)approximate Reimann’s solver’s technique is developed and validated with other research studies.Then many different scenarios including group of piers,group of groynes with different shapes and combination of groynes and piers are considered for dam break flow modeling.The final results showed that group of piers alone or group of groynes alone have no significant effects on the wave-front depth and celerity but,combination of L-head groyne with piers can decrease the amplitude and celerity of the dam break wavefront or flood wave.In this case,a blockage zone between the groynes and intensive backwater effects behind them were observed.

Modelling Dam Break Evolution over a Wet Bed with Smoothed Particle Hydrodynamics: A Parameter Study

When investigating water flow in spillways and energy dissipation, it is important to know the behavior of the free surfaces. To capture the real dynamic behavior of the free surfaces is therefore crucial when performing simulations. Today, there is a lack in the possibility to model such phenomenon with traditional methods. Hence, this work focuses on a parameter study for one alternative simulation tool available, namely the meshfree, Lagrangian particle method Smoothed Particle Hydrodynamics (SPH). The parameter study includes the choice of equation-of-state (EOS), the artificial viscosity constants, using a dynamic versus a static smoothing length, SPH particle spatial resolution and the finite element method (FEM) mesh scaling of the boundaries. The two dimensional SPHERIC Benchmark test case of dam break evolution over a wet bed was used for comparison and validation. The numerical results generally showed a tendency of the wave front to be ahead of the experimental results, i.e. to have a greater wave front velocity. The choice of EOS, FEM mesh scaling as well as using a dynamic or a static smoothing length showed little or no significant effect on the outcome, though the SPH particle resolution and the choice of artificial viscosity constants had a major impact. A high particle resolution increased the number of flow features resolved for both choices of artificial viscosity constants, but at the expense of increasing the mean error. Furthermore, setting the artificial viscosity constants equal to unity for the coarser cases resulted in a highly viscous and unphysical solution, and thus the relation between the artificial viscosity constants and the particle resolution and its impact on the behavior of the fluid needed to be further investigated.

A Dam Break Analysis Using HEC-RAS

This paper firstly described the dam break in the aspects of theories and models. Break parameters prediction, the understanding of dam break mechanics, peak outflow prediction were shown as the essential for the dam break analysis, and eventually determined the loss of the damages. Secondly, as an application example, Foster Joseph Sayers Dam break was further modeled and analyzed using USACE Hydrologic Engineering Center’s River Analysis System (HEC-RAS) model based on available geometry data. The results show that dam break is a complicated and comprehensive process involving lots of principles. Combination of mechanics and case studies, reflection of predominant mechanisms of headcut erosion, more specific categorization of dam, prudent investigation and inference of dam break process are needed in developing a satisfactory dam break simulation model. Foster Joseph Sayers Dam break due to piping elongates the time period of high water surface level, which increases the duration of risk. However, the dam break does not increase the downstream maximum water surface elevation (Max. W.S. Elev) significantly at previous design Probable Maximum Flood (PMF). Dam break has a greater impact on the downstream location where is closer to the dam in accordance with the comparison of the hydrographs at different downstream locations. Sensitivity analysis demonstrates that the changes of dam break parameters had no much influence on the downstream Max. W.S. Elev.

Coupling effect analysis of dam break flood spread and building collapse based on numerical simulation

Large-scale floods induced by dam failures could cause significant structural damage to buildings and massive loss of life.The coupling effect of large-scale flood spread and building collapse has complex impacts on the entire flow field,affecting flood risk assessment and building vulnerability evaluation.In this paper,a dynamic elevation change model designed to seamlessly interface with a structural vulnerability assessment model to investigate the interaction effect between floods and buildings is presented.The efficiency of the framework was validated by reconstructing the Gleno Dam-Break flood in Italy.Subsequently,a hydrodynamic model of the Jinsha-Yalong River that considers dynamic building collapse was established.The proposed model was compared with two traditional building treatment approaches and one that ignored the buildings.The results show that the interaction between the flood and buildings decreases the low-velocity area(below 1 m/s)by 7.44%-9.56%while increasing the high velocity area(above 4 m/s)by 10.71%-11.96%.Traditional and neglecting building treatments provide preliminary insights into densely built areas,and the latter could be an alternative for simplification because it can represent the worst-case scenario.Building collapse in response to large-scale floods typically occurs in four stages:flood spread,rapid expansion,gradual expansion,and flood recession.This analysis offers novel perspectives on flood prediction and simulations where the floodplain may contain buildings.This method could be useful for assessing structural vulnerability associated with large building stocks and developing flood mitigation strategies in densely populated areas.

Numerical Simulation of Dam-Break Flows Using Radial Basis Functions: Application to Urban Flood Inundation

Dam-break flows pose significant threats to urban areas due to their potential for causing rapid and extensive flooding. Traditional numerical methods for simulating these events struggle with complex urban landscapes. This paper presents an alternative approach using Radial Basis Functions to simulate dam-break flows and their impact on urban flood inundation. The proposed method adapts a new strategy based on Particle Swarm Optimization for variable shape parameter selection on meshfree formulation to enhance the numerical stability and convergence of the simulation. The method’s accuracy and efficiency are demonstrated through numerical experiments, including well-known partial and circular dam-break problems and an idealized city with a single building, highlighting its potential as a valuable tool for urban flood risk management.

Dam-break Flood Simulation under Various Likely Scenarios and Mapping Using GIS:Case of a Proposed Dam on River Yamuna,India

The precision modeling of dam break floods can lead to formulation of proper emergency action plan to minimize flood impacts within the economic lifetime of the assets.Application of GIS techniques in integration with hydrological modeling for mapping of the flood inundated areas can play a momentous role in further minimizing the risk and likely damages.In the present study,dam break analysis using DAMBRK model was performed under various likely scenarios.Probable Maximum Flood (PMF)calculated for a return period of 1000 years using deterministic approach was adopted for dam break analysis of the proposed dam under various combinations of breach dimensions.The available downstream river cross-sections data sets were used as input in the model to generate the downstream flood profile.Dam break flow depths generated by the DAMBRK model under various combinations of structural failure are subsequently plotted on Digital Elevation Model(DEM)of the downstream of dam site to map the likely affected area.The simulation results reveals that in one particular case the flood without dam may be more intense if a rainfall of significant intensity takes place.

Numerical Study of Dam-Break Induced Tsunami-Like Bore with A Hump of Different Slopes

Numerical simulation of dam-break wave, as an imitation of tsunami hydraulic bore, with a hump of different slopes is performed in this paper using an in-house code, named a Constrained Interpolation Profile （CIP）-based model. The model is built on a Cartesian grid system with the Navier Stokes equations using a CIP method for the flow solver, and employs an immersed boundary method （IBM） for the treatment of solid body boundary. A more accurate interface capturing scheme, the Tangent of hyperbola for interface capturing/Slope weighting （THINC/SW） scheme, is adopted as the interface capturing method. Then, the CIP-based model is applied to simulate the dam break flow problem in a bumpy channel. Considerable attention is paid to the spilling type reflected bore, the following spilling type wave breaking, free surface profiles and water level variations over time. Computations are compared with available experimental data and other numerical results quantitatively and qualitatively. Further investigation is conducted to analyze the influence of variable slopes on the flow features of the tsunami-like bore.

Experimental Investigation on the Interactions Between Dam-Break Flow and a Floating Box

An experiment that investigates the interactions between dam-break flow and a floating box is reported in this paper.The interaction processes are described in detail,and the effects of reservoir depth,clearance between the structure and vertical wall,and structure motion on the observed interactions are discussed.Results indicate that interactions are mild if the reservoir depth is relatively small and most of the water flows through under the structure.However,as the reservoir depth increases,the interactions intensify,and overtopping and wave splashing occur.The incident wave is divided into two parts by the structure:1)a jet generated by wave impact and 2)the water flowing through under the structure.The water flowing through under the structure is the main factor influencing the motion of the structure.The phenomenon of secondary slamming is observed in all of the test cases,and the relative motion of the structure and free surface explains the occurrence of secondary slamming.

Draining Tangjiashan Barrier Lake after Wenchuan Earthquake and the flood propagation after the dam break

Tangjiashan Barrier Lake is one of the largest barrier lakes caused by the Wenchuan Earthquake. Its risk analysis, emergency plan and effect of the emergency plan are introduced in this paper. The dam height of Tangjiashan Barrier Dam is about 105 m, and the reservoir storage capacity is 3.2×108 m3. When the dam broke the flood peak were estimated to be larger than 48000 m3/s, which might cause a enormous disaster to the downstream cities and residents. A discharge channel with 13 m deep and 8 m wide was drug, so that the water may flow out of the lake before the dam breaks. As a result, the drainage and risk mitigation project are successful. During the drainage process, the flood peak was about 6500 m3/s, and about 1.6×108 m3 of water was drained off and the residual reservoir capacity was only 8.97×107 m3. A new channel with average width 100 m was formed, which can bear floods of 200 years frequency. The successful experience and the collected data can be used to deal with the similar natural disasters in future.

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.

Numerical Simulation of Dam-Break Flooding of Cascade Reservoirs

Previous studies at home and abroad have mainly focused on single dam-break, and little attention has been paid so far to the dam-break of cascade reservoirs. Multi-source flooding, which can lead to three-dimensional turbulent phenomena and superposition effects, is the main difference between the dam-break of cascade and single reservoirs. Detailed descriptions of the coupled numerical simulation of multi-source flooding have little been reported, and the initial wet riverbed is rarely considered in current models. Therefore, in this paper, a method based on the three-dimensional (Formula presented.) turbulence model coupled with the volume-of-fluid method is proposed to simulate the dam-break flooding of cascade reservoirs. The upstream river, reservoir, and downstream river are connected by the internal boundary method, and the initial conditions, including river flow and reservoir water, are determined according to the results of the numerical simulation. Coupled numerical simulation of different dam-break flooding is then achieved. The present work solves the challenges presented by the enhancement and superposition of natural river flow, upstream flooding, and downstream flooding. This paper provides a theoretical basis for future studies on the dam-break flood routing of cascade reservoirs. © 2017 Tianjin University and Springer-Verlag GmbH Germany

Analysis of seismic disaster failure mechanism and dam-break simulation of high arch dam

Based on a Chinese national high arch dam located in a meizoseismal region, a nonlinear numerical analysis model of the damage and failure process of a dam-foundation system is established by employing a 3-D deformable distinct element code(3DEC) and its re-development functions. The proposed analysis model considers the dam-foundation-reservoir coupling effect, infl uence of nonlinear contact in the opening and closing of the dam seam surface and abutment rock joints during strong earthquakes, and radiation damping of far fi eld energy dissipation according to the actual workability state of an arch dam. A safety assessment method and safety evaluation criteria is developed to better understand the arch dam system disaster process from local damage to ultimate failure. The dynamic characteristics, disaster mechanism, limit bearing capacity and the entire failure process of a high arch dam under a strong earthquake are then analyzed. Further, the seismic safety of the arch dam is evaluated according to the proposed evaluation criteria and safety assessment method. As a result, some useful conclusions are obtained for some aspects of the disaster mechanism and failure process of an arch dam. The analysis method and conclusions may be useful in engineering practice.

Life Loss Estimation Based on Dam-Break Flood Uncertainties and Lack of Information in Mountainous Regions of Western China

Compared with urban floods, dam-break floods are associated with greater uncertainties, including variable dam-break modes and hydrological characteristics, so conventional flood estimation methods cannot be directly applied in the estimation of dam-break flood loss. In particular, there is scant information regarding the conditions of affected area and hydrological characteristics in southwest China. In this paper, we introduce an integrated model for estimating flood loss that is adapted to the mountainous regions of southwestern China in light of the relative lack of available information. This model has three major components: a basic information model, a dam-routed flood propagation simulation model, and a loss estimation model. We established the basic information model despite the relative lack of available information using 3S technology [remote sensing (RS); geographical information system (GIS); global positioning system (GPS)], data mining technology, and statistical analysis techniques. Our dam-routed flood propagation simulation model consists of major hydrologic processes and their governing equations for flow propagation, which we solve using finite-difference schemes. In this model, the flood propagation area is divided into grids and each grid is determined by the characteristic parameters obtained from the propagation simulation. We present a case study of the Lianghekou hydropower station in Sichuan Province, China to illustrate the practical application of this integrated model for life loss estimation. © 2017, Tianjin University and Springer-Verlag Berlin Heidelberg.

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.

Comparison of depth-averaged concentration and bed load flux sediment transport models of dam-break flow

This paper presents numerical simulations of dam-break flow over a movable bed. Two different mathematical models were compared: a fully coupled formulation of shallow water equations with erosion and deposition terms(a depth-averaged concentration flux model), and shallow water equations with a fully coupled Exner equation(a bed load flux model). Both models were discretized using the cell-centered finite volume method, and a second-order Godunov-type scheme was used to solve the equations. The numerical flux was calculated using a Harten, Lax, and van Leer approximate Riemann solver with the contact wave restored(HLLC). A novel slope source term treatment that considers the density change was introduced to the depth-averaged concentration flux model to obtain higher-order accuracy. A source term that accounts for the sediment flux was added to the bed load flux model to reflect the influence of sediment movement on the momentum of the water. In a onedimensional test case, a sensitivity study on different model parameters was carried out. For the depth-averaged concentration flux model,Manning's coefficient and sediment porosity values showed an almost linear relationship with the bottom change, and for the bed load flux model, the sediment porosity was identified as the most sensitive parameter. The capabilities and limitations of both model concepts are demonstrated in a benchmark experimental test case dealing with dam-break flow over variable bed topography.

尾矿的特性、灾害及其资源潜力

尾矿是矿石磨细选别后残余的固体废弃物,尾矿物理化学特性及尾矿库的常规地表堆存共同导致尾矿库存在较大的安全与环境风险。低品位矿体高强度开采趋势下,我国尾矿年排放量维持在10亿t以上的高位,累计堆存规模超200亿t,细粒尾矿堆存方式、潜在灾害防治及综合利用面临新挑战,采选新技术装备及政策利好因素推动尾矿资源潜力亟待释放。因此,以尾矿物理化学特性、排放堆存方法、溃坝灾害、尾矿资源潜力为主线,综述了尾矿物理化学特性、尾矿堆存形式、尾矿溃坝灾害防治等方面的研究进展,系统梳理了尾矿空区充填、尾矿制备材料、尾矿二次利用、超积累植物提取金属元素、尾矿固碳等资源综合利用方法,可为研究者及工业界系统全面地重新审视尾矿废弃物特性、尾矿库灾害防治、矿产可持续开发利用提供启示。

融合案例挖掘与贝叶斯网络的溃坝事故致因风险分析

为了更加深入、全面探究溃坝事故致因风险发生机理,提出了融合历史溃坝事故案例挖掘与贝叶斯网络的溃坝事故致因风险计算方法。该方法在采集国内外大量历史溃坝事故案例的基础上,采用24Model识别和提取溃坝事故致因及致因链,构建了溃坝事故致因拓扑结构,利用贝叶斯正向因果推理计算了溃坝发生概率,并结合反向诊断推理分析溃坝成因机理,基于贝叶斯敏感性分析挖掘影响溃坝关键风险因素。结果表明:在人为因素方面,闸门控制问题比例较高;在管理因素方面,施工问题、运维管理缺陷、设计问题是溃坝重要间接诱因;洪水漫顶、渗透侵蚀和渗透管涌是导致溃坝的主要风险因素。

利比亚德尔纳2023年极端洪水模拟复盘分析

全球气候变化背景下,极端强降雨和洪涝等水文事件的极值屡屡刷新历史记录,造成重大损失。2023年9月10—11日,在地中海飓风“丹尼尔”的影响下,利比亚东北部地区发生罕见特大暴雨,引发德尔纳市上游两座水库接连溃决,造成巨大人员伤亡。本文对德尔纳市极端洪水事件进行了梳理,并以德尔纳市洪灾及受影响区域为研究对象,建立了二维水动力模型,对溃坝洪水进行了模拟和复盘分析。通过哥白尼应急管理服务(Copernicus Emergency Management Service,CEMS)提供的受灾数据对模型结果进行对比验证(CEMS持续监测欧洲和全球即将发生或实时发生的灾难事件)。结果显示,影响德尔纳市的溃坝洪水持续了2 h左右,对城市的破坏主要集中在前30 min。本次复盘分析了德尔纳市溃坝洪水演进与风险分布特征,可为我国城市地区大坝溃决风险防控、早期预警和应急管理提供参考借鉴,同时也可为世界其他地区的大坝溃决风险防控、早期预警和应急管理提供参考借鉴。