Dam-break Simulation Research Articles

Wave generation and wave–structure impact modelling with WCSPH

The reliable prediction of plunging wave induced load, which represents a challenging task in offshore engineering, is of key relevance for the safety of existing offshore structures as well for the reliable design of new ones. This work shows the early advances in the development of a FOSS derived model, obtained by independently introducing relevant modifications in the original model SPHERA v.9.0.0 (RSE SpA) based on the Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) method. This derived model is validated on single-phase laboratory flume tests from technical literature (i.e., dam break and regular waves) and on a laboratory flume test of plunging wave impacting an offshore structure. The derived model allows modelling two-phase flows with a large density ratio, as shown by an additional two-phase dam break simulation. Therefore it seems promising for application to two-phase plunging impact to improve the prediction of impact load on the structure.

Investigation of Under-Relaxation Factors in 2D Dam Break Simulation of OpenFOAM®

Computational fluid dynamics (CFD) is one of the most significant applied sciences in the industry. For this reason, many expensive CFD software is available in the market. OpenFOAM® is a free CFD software that has been used extensively in many ranges of fields. But, even with the free charge, it is still hard to get a good result with OpenFOAM® without extensive computational resources. This study aims to find a way to get good results with minimum computation time by investigating the under-relaxation effects. This study chose the dam break case due to its simple and readily available validation data. The simulation domain was a 200 × 200 mm2 dam filled with 50 × 100 mm2 water in the dam’s bottom left corner. The simulations were performed with under-relaxation factors, ranging from 0.3 to 1. By changing the under-relaxation factor to 0.95, the mean absolute percentage error became six times smaller, and the simulation was 366 times faster. It shows that the under-relaxation factor is essential in the quality of results and simulation time. However, the most optimal under-relaxation factor may differ from one case to another.

Lethe-DEM: an open-source parallel discrete element solver with load balancing

Approximately $${75}\%$$ of the raw material and $${50}\%$$ of the products in the chemical industry are granular materials. The discrete element method (DEM) provides detailed insights of phenomena at particle scale, and it is therefore often used for modeling granular materials. However, because DEM tracks the motion and contact of individual particles separately, its computational cost increases nonlinearly $$O(n_\mathrm{p}\log (n_\mathrm{p}))$$ – $$O(n_\mathrm{p}^2)$$ (depending on the algorithm) with the number of particles ( $$n_\mathrm{p}$$ ). In this article, we introduce a new open-source parallel DEM software with load balancing: Lethe-DEM. Lethe-DEM, a module of Lethe, consists of solvers for two-dimensional and three-dimensional DEM simulations. Load balancing allows Lethe-DEM to significantly increase the parallel efficiency by $$\approx {25}$$ – $${70}\%$$ depending on the granular simulation. We explain the fundamental modules of Lethe-DEM, its software architecture, and the governing equations. Furthermore, we verify Lethe-DEM with several tests including analytical solutions and comparison with other software. Comparisons with experiments in a flat-bottomed silo, wedge-shaped silo, and rotating drum validate Lethe-DEM. We investigate the strong and weak scaling of Lethe-DEM with $${1}\le n_\mathrm{c} \le {192}$$ and $${32}\le n_\mathrm{c} \le {320}$$ processes, respectively, with and without load balancing. The strong-scaling analysis is performed on the wedge-shaped silo and rotating drum simulations, while for the weak-scaling analysis, we use a dam-break simulation. The best scalability of Lethe-DEM is obtained in the range of $${5000}\le n_\mathrm{p}/n_\mathrm{c} \le {15{,}000}$$ . Finally, we demonstrate that large-scale simulations can be carried out with Lethe-DEM using the simulation of a three-dimensional cylindrical silo with $$n_\mathrm{p}={4.3}\times 10^6$$ on 320 cores.

Granular Flow–Obstacle Interaction and Granular Dam Break Using the S-H Model with the TVD-MacCormack Scheme

An accurate second-order spatial and temporal finite-difference scheme is applied to solve the dynamics model of a depth-averaged avalanche. Within the framework of the MacCormack scheme, a total variation diminishing term supplements the corrector step to suppress large oscillations in domains with steep gradients. The greatest strength of the scheme lies in its high computational efficiency while maintaining satisfactory accuracy. The performance of the scheme is tested on a granular flume flow–obstacle interaction scenario and a granular dam breaking scenario. In the former, the flume flow splits into two granular streams when an obstacle is encountered. The opening between the two granular streams widens when the side length of the obstacle increases. In the simulation, shock waves with a fan-shaped configuration are captured, and successive waves in the tail of the avalanche between the two streams are observed. In the latter scenario, the average values and the fluctuations in the flow rate and velocity (at relatively steady state) decrease with the width of the breach. The capture of complex and typical granular-flow phenomena indicates the applicability and effectiveness of combining the TVD-MacCormack Scheme and S-H model to simulate dam breaking and inclined flow–obstacle interaction cases. In this study, the dense granular flow strikes on a rigid obstacle that is described by a wall boundary, rather than a topographic feature with a finite slope. This shows that the TVD-MacCormack scheme has a shock-capturing ability. The results of granular dam break simulations also revealed that the boundary conditions (open or closed) affect the collapse of the granular pile, i.e., the grains evenly breached out under closed boundary conditions, whereas the granules breaching out of the opening were mostly grains adjacent to the boundaries under open boundary conditions.

Hypothetical failure of the Khassa Chai dam and flood risk analysis for Kirkuk, Iraq

Many of Iraqi's high-hazard dams lack an Emergency Action Plan, which should include a flood inundation map to show which downstream areas would be flooded if the dams were to fail. This article presents the results of the simulation of a hypothetical 2D dam break for the 58 m high Khassa Chai dam in Kirkuk, Iraq, using HEC-RAS 2D 5.0.7 software. The Khassa Chai dam is situated 7.4 km north of Kirkuk. The simulations revealed that the dam-break flood will affect eight major bridges and the majority of Kirkuk city's metropolitan neighborhoods. Within an hour, the floodwaters will reach the city's center. The flood hazard map revealed that if the Khassa Chai dam fails, many people, vehicles, and structures will be at danger. The findings of this paper can be used to identify evacuation routes and refuge sites as well as build suitable warning systems in order to limit the risk for fatalities if the Khassa Chai dam fails. Moreover, as the effect of modeling bridges downstream of failed dams has not been explored yet, to the knowledge of the authors, eight bridges have been modeled. It was concluded that ignoring bridges in such a large dam break model will not affect the results significantly, which saves the time of data collection and model development.

A practical probabilistic approach for simulating life loss in an urban area associated with a dam-break flood

Dam safety simulation is crucial to design and improve emergency plans to mitigate the flood disaster risk associated with break events, particularly in the areas located downstream. Applying deterministic estimation of the peak flow has some limitations for deciding in terms of uncertainty. In this study, we proposed an integrated approach based on Monte Carlo Simulation (MCS), HEC-RAS 2D, and HEC-LifeSim models to simulate dam break to deal with the flood risk with probability rather than analyzing a few dam break scenarios. This approach was applied to simulate a dam break event and its impact on Life Loss (LL) according to 12 alternatives in Sidi Yahya Zaer town, in Morocco. The results showed that for dam-break peak flows associated with Exceedance probabilities of 1%, 5%, 10%, 50%, 90%, and 95% the mean of the simulated LL are ranging from 2 to 334 people at night time and from 2 to 173 people at day time. They exponentially depend on dam-break peak flows. Furthermore, the comparison of the LL results with those of the historic events showed that a fatality of 125 people that was occurred by the Buffalo Creek dam break in the USA (1972) is possible in SYZ town with a probability of 9.2%. Globally, the proposed methodology is valuable to evaluate the dam-break consequences associated with a probability. Also, it can be reproduced to evaluate the vulnerability of the future urbanized areas not only to flood disasters but to other natural and industrial disasters.

Gas/Liquid Two-Phase Flow in Pipes: Slugs, Classical Flow-Map, and 1D Compositional Simulation

SummaryIn this paper, I present numerical results of gas/liquid flows in pipelines obtained from a new simulation code. One difference, with respect to other 1D fluid dynamic commercial simulation products, is the use of a compositional approach to the problem: This is rarely found in published articles about gas/liquid flow in the oil and gas industry. It is shown that the algorithm can calculate both pressure and material fast waves generated during the transportation of gas and liquid in pipes. The solution algorithm is based on the application of a two-fluid model to the mass, momentum, and energy conservation equations, which are solved using a mixed implicit-explicit integration schema. Closure equations for the calculation of interface stress are taken from literature articles. A dam-break simulation (i.e., a Riemann initial value problem) is presented as a severe test case for validation of the two-phase flow algorithm. Because the code is able to capture sharp and fast changes in the liquid holdup connected to the formation of pressure waves, it is applied to the simulation of slug flow without the use of steady-state “unit cell” models and slug tracking functions. In this context, the experimental results on pseudoslug formation in inclined pipes at high pressures, published by the Tulsa University Fluid Flow Project (TUFFP), are used to compare simulated results with experimental data. The last part is dedicated to the simulation of some cases taken from a classical flow-map of a fundamental article by Taitel and Dukler (1976). At constant liquid superficial velocity, the formation of liquid slugs and their subsequent termination with the increase of gas flow rate is simulated with details never previously presented.

Visual Simulation of Soil-Structure Destruction with Seepage Flows

This paper introduces a method for simulating soil-structure coupling with water, which involves a series of visual effects, including wet granular materials, seepage flows, capillary action between grains, and dam breaking simulation. We develop a seepage flow based SPH-DEM framework to handle soil and water particles interactions through a momentum exchange term. In this framework, water is seen as a seepage flow through porous media by Darcy's law; the seepage rate and the soil permeability are manipulated according to drag coefficient and soil porosity. A water saturation-based capillary model is used to capture various soil behaviors such as sandy soil and clay soil. Furthermore, the capillary model can dynamically adjust liquid bridge forces induced by surface tension between soil particles. The adhesion model describes the attraction ability between soil surfaces and water particles to achieve various visual effects for soil and water. Lastly, this framework can capture the complicated dam-breaking scenarios caused by overtopping flow or internal seepage erosion that are challenging to simulate.

Simulation of Three-Dimensional Free-Surface Dam-Break Flows over a Cuboid, Cylinder, and Sphere

AbstractA three-dimensional (3D) numerical study is undertaken to investigate dam-break flows over 3D structures. A two-phase flow model has been developed within the large-eddy simulation (LES) fr...

FLOOD INUNDATION AND DAM BREAK ANALYSIS FOR DISASTER RISK MITIGATION (A CASE STUDY OF WAY APU DAM )

This paper presents a numerical modeling to simulate flood inundation and dam break analysis of Way Apu dam for an emergency action plan (EAP), by considering EAP guidelines for ICOLD (International Committee on Large Dam). The Way Apu dam, located in Way Apu River, Maluku, Indonesia is a multi-purpose dam constructed mainly for irrigation, hydropower, water supply, and flood control. Therefore, the dam’s outflow discharge needs to be analyzed, due to the large amount of rainfall in eastern Indonesia. Thus, there is a need to analyze flood inundation mapping and dam break simulation in a bid to identify the flood mitigation risk zone and early warning system, within the downstream area of Way Apu dam. In this study, the flood inundation mapping and dam break simulation were analyzed using HEC-RAS 5.0.7. The analysis results of flood routing generate the outflow peak discharge reduction over spillway were 7.36 % (Ten years return period discharge, Q10) and just 2.14% (Probable maximum flood discharge, QPMF), indicating the simulation results of Hec-Ras 5.0.7 model for conditions with or without dam break did not show significant difference in dam’s downstream area. According to these results, 6 sub-districts are affected by the flood (Grandeng, Waeleman, Wanakarta, Waenetat, Debowae, Mako) with a maximum flood height range between 1-2.5 m (Q10) and 2.9-4.2 m (QPMF). The simulation results of arrival time also showed the estimation of evacuation time for QPMF ranges from 6 - 12 hours.

Finding an Optimum Grid Size for Numerical Simulations of Dam-break Flow Using Open-Access Digital Elevation Models

This work presents numerical simulations for dam-break flow with open-access digital elevation models (DEMs). The objective is to find an optimum grid size for the simulations in terms of accuracy and computational cost. A hypothetical breaching case of Batutegi dam in Indonesia was selected as a case study. Three DEM types with different spatial resolutions, i.e. MERIT-Hydro (∼90 m), ALOS (∼30 m), and DEMNAS (∼8.1 m), were employed. For each DEM, the numerical simulations were performed using four grid sizes, from the lowest to the finest resolution, i.e. 200 m, 90 m, 50 m, and 20 m. All simulations were carried out on a desktop consisting of 10 cores/20 threads with an in-house code NUFSAW2D, enabling parallelization, where double precision arithmetic was used. It was observed that using the computational grid size finer than 50 m produces no longer significant differences of the maximum inundation boundary, maximum depth, maximum velocity, and average depth. This study would be useful for engineers and decision makers, when performing dam-break simulations using DEMs in a framework of an early-warning system.

Comparison of Taylor Galerkin and FTCS models for dam-break simulation

The aim of this paper is to compare the ability of two numerical models to simulate two-dimensional dam-break flows. Dam-break modelling is important in reducing the high-risk of dam failure by determining the water flow movement and its effect on buildings downstream. In this study, the Taylor Galerkin and Forward Time Central Space method is presented to simulate 2-D dam-break flow. The Hansen filter is applied to both methods to reduce numerical instability oscillations in the model. The filters were used for each time step at each computing point. The model is verified by comparing the result simulation with numerical results from previous studies. The result show that Taylor Galerkin numerical scheme with Hansen filter is successful to simulate the problem of 2-D dam-break. Also, the Taylor Galerkin model has better results than the FTCS model. Studies like this are needed for mitigation efforts in the event of dam failure.

Weakly compressible Navier-Stokes solver based on evolving pressure projection method for two-phase flow simulations

An evolving pressure projection method for numerical computations of the weakly compressible Navier-Stokes equations is proposed. Fully explicit time integration is achieved using an independent pressure evolution equation. To damp the acoustic wave in a weakly compressible fluid flow, we iteratively compute the pressure evolution equation coupled with a projection step. Due to the simplicity and locality of this iteration procedure, it does not increase the computational amount too much. The computation is performed on a staggered Cartesian grid. By introducing the phase field model for interface capturing, this solver can be directly applied to two-phase flow simulations using a one-fluid model. Exact mass conservation is ensured by a finite-volume formulation of the conservative phase field equation. Various benchmarking problems are simulated to validate accuracy. The stability of a violent two-phase flow with large density and viscosity ratio is demonstrated in a three-dimensional dam break simulation. Numerical results show that the proposed method for weakly compressible Navier-Stokes equations can prevent oscillations of pressure and velocity.

Dam-Break analysis: proposal of a simplified approach

ABSTRACT Simplified methods are useful alternatives for prior analysis of the effects of dam rupture and can guide the decision-making process for carrying out more complete studies. In this context, a new simplified approach is presented, which enables the analysis of aspects from dam rupture of earthen dams that failed due to overtopping, considering dam height and reservoir volume as input data. Hypothetical cases were analyzed applying dam-break hydrodynamic simulations, which results allowed the development of equations capable of estimating peak flow attenuation and peak discharge arrival time along the downstream valley. The proposed approach was applied in a hypothetical case study (15 m high dam and 17 hm3 reservoir volume), obtaining results close to those achieved through other methods, especially in case of estimating the maximum discharges throughout the downstream valley, where the average differences between the results of the methods were of the order of 15%.

Numerical study of shallow-water equations using three explicit schemes - application to dam break flood wave

The numerical method to solve dam break problem on regular bathymetry was developed. Two cases of dam break wave propagation on wet and dry bottoms were selected to verify the numerical model elaborated. Three numerical schemes of Lax-Friedrichs, Adams-Bashforth and Adams-Bashforth-Adams-Moulton are applied to simulate this phenomenon using the 1D Saint-Venant equations. An artificial viscosity is added to these numerical schemes to provide stability and reduce numerical diffusion. This viscosity makes the numerical scheme robust (very powerful) for the simulation of this phenomenon. The results obtained show that these developed models are able to simulate dam break wave propagation process. The relative error in the L1 norm between the computed results and analytical solutions is calculated. The L1 norm indicates that the Adams-Bashforth-Adams-Moulton scheme has better accuracy than the other two schemes. It is shown that the technique used is simple, accurate, robust and stable for the simulation of the dam break wave propagation on wet and dry bed conditions.

Vertically Averaged and Moment Equations for Dam-Break Wave Modeling: Shallow Water Hypotheses

The dam-break wave modeling technology relies upon the so-called shallow water equations (SWE), i.e., mass and momentum vertically averaged equations by implementing the shallow water hypotheses, namely (i) horizontal velocity component independent of the vertical coordinate, (ii) vertical velocity component is null, (iii) pressure distribution is hydrostatic, (iv) turbulence is neglected. While this model often yields a satisfactory answer from an engineering standpoint, flows with vertical length scales not negligible cannot be modeled with accuracy, including the undular surge generated after a dam break for relatively high tailwater levels. These flows are modeled by the Serre–Green–Naghdi equations (SGNE), which fail to mimic wave breaking for low tailwater levels, however. Neither SWE nor SGNE produce a fully satisfactory answer for modeling dam break waves, therefore. A higher-order model using vertically averaged and moment equations (VAM) is used in this work to simulate dam break waves, thereby showing good results for arbitrary values of the tailwater level. The model contains four perturbation parameters implemented to overcome the shallow water hypotheses; two for the velocity components and two for fluid pressure. The role of each parameter in relaxing the limitations of the SWE is systematically investigated, depicting a complex and necessary interplay between the dynamic component of fluid pressure and the modeling of the velocity profile in producing accurate solutions for both non-hydrostatic and broken waves in dam break flows. The results highlight how the shallow water hypotheses can be relaxed in the vertically averaged modeling of dam break waves, producing an outcome of both theoretical and practical interest in the field. The results generated are tested with available experimental data, resulting in acceptable agreement.

Fluid-elastic structure interaction simulation by using ordinary state-based peridynamics and peridynamic differential operator

The fluid-structure interaction phenomenon is often encountered in the ocean engineering field. In the present work, a non-local numerical model is developed for the simulations of weakly compressible viscous fluid and elastic structure interactions. The peridynamic theory is adopted for both the structure and fluid modelling. The elastic structure is described by using the ordinary state-based peridynamics, while the fluid is modelled by utilizing the peridynamic differential operator. Furthermore, the updated Lagrangian description is adopted for the fluid including the relative deformation gradient expressed by the peridynamic differential operator. The fluid-structure interface and its normal direction are calculated via the gradient of a colour function, which varies with the fluid motion and structure deformation. Besides, the interaction force exerted from fluid to structure is constrained to be always perpendicular to the moving interface. Hence the fluid motion and structural deformation are predicted simultaneously. The validation of the developed model is conducted through the simulation of a water dam break with a rubber gate. The good agreement between the peridynamic and the experiment results demonstrates the capability of the current model for solving fluid-elastic structure interaction problems.

Multibody Dynamics Versus Fluid Dynamics: Two Perspectives on the Dynamics of Granular Flows

Abstract Considering that granular material is second only to water in how often it is handled in practical applications, characterizing its dynamics represents a ubiquitous problem. However, studying the motion of granular material poses stiff computational challenges. The underlying question in this contribution is whether a continuum representation of the granular material, established in the framework of the smoothed particle hydrodynamics (SPH) method, can provide a good proxy for the fully resolved granular dynamics solution. To this end, two approaches described herein were implemented to run on graphics processing unit (GPU) cards to solve the three-dimensional (3D) dynamics of the granular material via two solution methods: a discrete one, and a continuum one. The study concentrates on the case when the granular material is packed but shows fluid-like behavior under large strains. On the one hand, we solve the Newton–Euler equations of motion to fully resolve the motion of the granular system. On the other hand, we solve the Navier–Stokes equations to describe the evolution of the granular material when treated as a homogenized continuum. To demonstrate the similarities and differences between the multibody and fluid dynamics, we consider three representative problems: (i) a compressibility test (highlighting a static case); (ii) the classical dam break problem (highlighting high transients); and (iii) the dam break simulation with an obstacle (highlighting impact). These experiments provide insights into conditions under which one can expect similar macroscale behavior from multibody and fluid dynamics systems governed by manifestly different equations of motion and solved by vastly different numerical solution methods. The models and simulation platform used are publicly available and part of an open source code called Chrono. Timing results are reported to gauge the efficiency gains associated with treating the granular material as a continuum.

Multiphase particle method using an elastoplastic solid phase model for the diffusion of dumped sand from a split hopper

It is necessary to accurately predict the diffusion and deposition range of a large amount of sand dumped from a hopper barge for efficient reclamation in a coastal area. Many previous studies have proposed useful models to simulate the diffusion behavior of sand in fluid; however, most of their models have not considered the deposition of sand. This study proposes a particle-based numerical model that includes fluid-sand interaction. The model utilizes two methods to track the sand: an elastoplastic model for a sand layer and an advection-diffusion model for suspended sediments. These two techniques for sand tracking enable the evaluation of diffusion and deposition more accurately in a series of sand processes from inside the hopper to the seafloor. The proposed model was validated with a dam-break simulation using fluid and saturated sand. In this validation, the time histories of the runout distance of the dam-break flow and the final deposition shape of the sand were compared, and they agreed well with previous experimental results. Thereafter, we conducted an experiment in which sand was dumped from a split hopper, and the model was validated using the results of this experiment. The performance of the model was examined, focusing on the spread of the suspended sediments, the velocity field of the fluid, and the deposition of sand. The flow characteristics induced by the dumped sand were revealed from the calculated results.

Numerical Simulation and Risk Assessment of Cascade Reservoir Dam-Break

Despite the fact that cascade reservoirs are built in a large number of river basins nowadays, there is still an absence of studies on sequential embankment dam-break in cascade reservoirs. Therefore, numerical simulations and risk analyses of cascade reservoir dam-break are of practical engineering significance. In this study, by means of contacting the hydraulic features of upstream and downstream reservoirs with flood routing simulation (FRS) and flood-regulating calculation (FRC), a numerical model for the whole process of cascade reservoir breaching simulation (CRBS) is established based on a single-embankment dam-break model (Dam Breach Analysis—China Institute of Water Resources and Hydropower Research (DB-IWHR)). In a case study of a fundamental cascade reservoir system, in the upstream Tangjiashan barrier lake and the downstream reservoir II, the whole process of cascade reservoir dam-break is simulated and predicted under working schemes of different discharge capacities, and the risk of cascading breaching was also evaluated through CRBS. The results show that, in the dam-break of Tangjiashan barrier lake, the calculated values of the peak outflow rate are about 10% more than the recorded data, which are in an acceptable range. In the simulation of flood routing, the dam-break flood arrived at the downstream reservoir after 3 h. According to the predicted results of flood-regulating calculations and the dam-break simulation in the downstream reservoir, the risk of sequential dam-break can be effectively reduced by setting early warnings to decrease reservoir storage in advance and adding a second discharge tunnel to increase the discharge capacity. Alongside the simulation of flood routing and flood regulation, the whole process of cascade dam-break was completely simulated and the results of CRBS tend to be more reasonable; CRBS shows the great value of engineering application in the risk assessment and flood control of cascade reservoirs as an universal numerical prediction model.