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In this article, the performances of the SPH method to solve Shallow Water Equations SWEs with three investigation parameters were studied, such as the type of kernel functions, namely: cubic spline, Gaussian and quintic spline kernels, the number of particles used and the stabilization terms injected, specifically: Lax Friedrichs flux, artificial viscosity and two shocks Riemann solver. Three benchmarking tests make the subject of unsteady free surface flow in this study. It is 1D typical dam-break on wet and dry bottom; 2D partial dam-break on a dry floodplain and 2D partial dam-break on channel with 90° bend. The analysis of the different errors between the numerical and analytical solutions and/or the experimental data shows that the SPH method gives reliable values with the selected optimal parameters which are the cubic kernel function and the artificial viscosity term. The increase in the number of particles increases the precision but also the calculation time. [ABSTRACT FROM AUTHOR]

Aiming at the issue of membership leaping that may occur in the conventional variable fuzzy evaluation method when dealing with exponential changing index, based on the improvement of the model, considering the fuzziness and randomness of the dam break life loss system, this manuscript promoted a model which could evaluate the human life loss caused by dam break flood. The relative difference formula was improved by logarithmic transformation and boundary constraint. The improved method was proved to be effective after applied to 4 reservoirs. The calculation result of the life loss rate and the risk level of life loss rate were consistent. This verified result and the promoted model can provide new ideas and new methods in the risk management of reservoir dams, and enrich and supplement the risk management theory. [ABSTRACT FROM AUTHOR]

Summary: Dam‐Break waves arise from the sudden release of the water stored behind a wall, and they cause destruction and losses on nearby areas. Characterisation of the impact force on obstacles is very important for risk assessment. In this work, we performed a series of lock‐release experiments to evaluate the wave‐induced impact force on a vertical end wall situated some distance from the lock. Laboratory data were used to evaluate the performance of several types of numerical models to predict the wave‐induced force on the vertical end wall. The selected models were as follows: the hydrostatic 1D De Saint‐Venant model, the multi‐layer hydrostatic model and the Navier–Stokes two‐phase flow. For the latter two models, both 2D (in the x‐ z plane) and 3D simulations were performed. The results show that, independently of the hydrostatic assumption, the 2‐D simulations generate nonphysical oscillations which are not present in the measured temporal histories of the pressure and force values. By contrast, the predictions of both 3D numerical models better reproduce the temporal variation of the pressure forces on the end wall. The present study also shows that from a practical point of view, the 1D De Saint‐Venant model predicts with sufficient accuracy the impact time and the magnitude of the peak value of the impact force. Therefore, if the use of a fully 3D models is not a feasible option, in terms of a trade‐off between computation cost and accuracy, the use of a simple hydrostatic 1D De Saint‐Venant model is preferable to a 2D model. [ABSTRACT FROM AUTHOR]

In this paper, we develop a mathematical model for modelling and simulation of the dam-break flow through various obstacles. The model used here is an extension of one-layer non-hydrostatic (NH-1L) model by considering varying channel width (Saint Venant). The capability of our proposed scheme to simulate free surface wave generated by dam-break flow through various obstacles is demonstrated, by performing two types of simulation with various obstacles, such as; bottom obstacle and channel wall contraction. It is shown that our numerical scheme can produce the correct surface wave profile, comparable with existing experimental data. We found that our scheme demonstrates the evolution of a negative wave displacement followed by an oscillating dispersive wave train. These well-captured dispersive phenomena, indicated both the appropriate numerical treatment of the dispersive term in our model and the performance of our model.

Assessment of flood damage caused by dam failures is typically performed deterministically on the basis of a single preselected scenario, neglecting uncertainties in dam-break parameters, exposure information, and vulnerability model. This paper proposes a probabilistic flood damage model for the estimation of life loss due to dam-break flooding with the aim of overcoming this limitation and performing a more comprehensive and informative evaluation of flood risk. The significant novelty lies in the fact that the model combines uncertainties associated with all three components of risk: hazard, exposure, and vulnerability. Uncertainty in flood hazard is introduced by considering a set of dam-break scenarios, each characterized by different breach widths and reservoir levels. Each scenario is linked to a probability, which is assumed conditional on the dam-break event. Uncertainty in exposure is accounted for using dasymetric maps of the population at risk for two socio-economic states (representing business and non-business hours of a typical week), along with associated likelihood. Vulnerability to flooding is described through a well-established empirical hazard-loss function relating the fatality rate of the population at risk to the flood hazard, the flood severity understanding, and the warning time; a confidence band provides quantitative information about the associated uncertainty. The probabilistic damage model was applied to the case study of the hypothetical collapse of Mignano concrete gravity dam (northern Italy). The main outcome is represented by probabilistic flood damage maps, which show the spatial distribution of selected percentiles of a loss-of-life risk index coupled with the corresponding uncertainty bounds. [ABSTRACT FROM AUTHOR]

This study proposes a numerical model for depth-averaged Reynolds equations (shallow-water equations) to investigate a dam-break problem, based upon a two-dimensional (2D) second-order upwind cell-centre finite volume method. The transportation terms were modelled using a modified approximate HLLC Riemann solver with the first-order accuracy. The proposed 2D model was assessed and validated through experimental data and analytical solutions for several dam-break cases on a wet and dry bed. The results showed that the error values of the model are lower than those of existing numerical methods at different points. Our findings also revealed that the dimensionless error parameters decrease as the wave propagates downstream. In general, the new model can model the dam-break problem and captures the shock wave superbly. [ABSTRACT FROM AUTHOR]

Cases of dam failures are seen almost every year globally, and the propagation of rapidly varying unsteady flows resulting from those dam failures has significant environmental and economic consequences. A three-dimensional Computational Fluid Dynamics model was created to solve unsteady Reynolds-Averaged equations to investigate the generation and propagation of dam-break flows and reflected flood waves in the presence of a trapezoidal bottom obstacle. The dam-breaks were modelled using OpenFOAM based on the Volume of Fluid method employing the Finite Volume Method, and the performance of various Reynolds-Averaged Navier-Stokes turbulence models, including the realizable k − ε, SST k − ω (Shear Stress Transport k − ω), and v2 − f models, has been evaluated. To assess the capabilities of the different turbulence models, quantitative comparisons of numerical simulations with laboratory experiments were completed, and it was found that the SST k − ω model performed better in predicting the free surface profiles and negative bore propagation speeds than the realizable k − ε and v2 − f models. [ABSTRACT FROM AUTHOR]

The silted-up sediment in the reservoir may have a significant influence on the propagation of dam-break flows. In this paper, a three-dimensional numerical simulation of the silted-up dam-break flow is carried out. In this paper, simulations of three-dimensional silted-up dam-break flow are carried out. A kind of Eulerian–Eulerian two-fluid model (TFM), coupled level set and volume of fluid (CLSVOF) methods, is presented. In order to calculate the motions of the air–water interface and the sediment simultaneously, kinetic particle theory (KPT) and computational fluid dynamics (CFD) are combined. The rheology-based constitutive equations of sediment are also considered to simulate scouring and deposition. In addition, a partial-slip boundary condition (BC) for the velocity of the sediment phase at stationary walls is implemented. The simulation results of the benchmark case demonstrate that the proposed model can effectively simulate the silted-up dam-break flow while taking into account multi-interface capturing problems. Subsequently, the simulations of the silted-up dam-break flow over dry are investigated numerically in a three-dimensional long channel. The simulated results reveal that, in the dam-break flows, the silted-up sediment height has a significant influence on wave propagation, dynamic pressure loads, sediment transport, and sediment deposition. HIGHLIGHTS Three-dimensional simulation of silted-up dam-break flow is carried out.; The air–water interface movement is captured by CLSVOF method.; A Eulerian–Eulerian multiphase model coupling kinetic particle theory and computational fluid dynamics is used.; The rheology-based constitutive equations of sediment are considered.; The effect of the silted-up sediment height during a dam-break flow is investigated.;

Historically, the occurrence of dam-break cases has been proven to cause significant loss of life and economical damage. Apart from the catastrophic nature of dam-breaks, the absence of a robust disaster prevention system exacerbates the disasters that can be occurred in any situations. Considering the importance of such prevention system, this study is therefore aimed to propose an Early Warning System (EWS) to mitigate the impact of dam-break disasters. However, predicting the occurrence of such disasters is challenging, specifically in areas like Indonesia, where comprehensive data recording is lacking. While it may be difficult to predict the occurrence of a sunny day break, the storm-induced break is more predictable. In this study, a simple yet effective macro-based EWS is proposed for Earth-Filled Dam-Break Cases using a macro approach based on the Evacuation Clearance Time (ECT). By comparing the ECT value with the arrival time of the floods from the affected areas, additional evacuation time can be obtained, which will be used to determine the EWS. Cengklik Dam, as one of the oldest dams in Indonesia that was constructed in 1931, is then chosen as the case study. The proposed EWS for Cengklik Dam is given in three levels of warning indicated by the reservoir water level at +141.36 m, +141.40 m, and +141.45 m. With the proposed EWS, the results show that 100% of people are expected to reach the evacuation point safely. The case study shows that the proposed EWS can significantly reduce the risk impact of the dam-break events. [ABSTRACT FROM AUTHOR]

Quantitative assessment of dam-break flood hazard is central in dam emergency action planning and is typically performed deterministically. In structural failure of concrete or masonry dams the collapse is assumed to be total and instantaneous, with the reservoir level at the spillway crest level. A probabilistic method is here proposed based on a set of dam-break scenarios characterized by different breach widths and reservoir levels in order to provide an appraisal of uncertainties in flood hazard indicators. Each scenario is attributed a weight, defined as a conditional probability given a dam-break event. Probabilistic flood hazard and inundation maps are produced for the case study of the hypothetical collapse of the Mignano dam (River Arda, northern Italy), and a sampling-based global sensitivity analysis is performed. Dam-break flooding was simulated using a two-dimensional hydrodynamic model on a high-resolution mesh. The probabilistic maps inherently provide quantitative information on the uncertainty of dam-break flood hazard. [ABSTRACT FROM AUTHOR]

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Adaptive interface-Mesh un-Refinement (AiMuR) based Sharp-Interface Level-Set-Method (SI-LSM) is proposed for both uniform and non-uniform Cartesian-Grid. The AiMuR involves interface location based dynamic un-refinement (with merging of the four control volumes) of the Cartesian grid away from the interface. The un-refinement is proposed for the interface solver only. A detailed numerical methodology is presented for the AiMuR and ghost-fluid method based SI-LSM. Advantage of the novel as compared to the traditional SI-LSM is demonstrated with a detailed qualitative as well as quantitative performance study, involving the SI-LSMs on both coarse grid and fine grid, for three sufficiently different two-phase flow problems: dam break, breakup of a liquid jet and drop coalescence. A superior performance of AiMuR based SI-LSM is demonstrated - the AiMuR on a coarser non-uniform grid ( N U c AiMuR ) is almost as accurate as the traditional SI-LSM on a uniform fine grid ( U f ) and takes a computational time almost same as that by the traditional SI-LSM on a uniform coarse grid ( U c ). The AMuR is different from the existing Adaptive Mesh Refinement (AMR) as the former involves only mesh un-refinement while the later involves both refinement and un-refinement of the mesh. Moreover, the proposed computational development is significant since the present adaptive un-refinement strategy is much simpler to implement as compared to that for the commonly used adaptive refinement strategies. The proposed numerical development can be extended to various other multi-physics, multi-disciplinary and multi-scale problems involving interfaces. [ABSTRACT FROM AUTHOR]

Historically, the occurrence of dam-break cases has been proven to cause significant loss of life and economical damage. Apart from the catastrophic nature of dam-breaks, the absence of a robust disaster prevention system exacerbates the disasters that occur. This study proposes an Early Warning System (EWS) to mitigate the impact of dam-break disasters. However, predicting the occurrence of such disasters is challenging, specifically in areas like Indonesia, where comprehensive data recording is lacking. While it may be difficult to predict the occurrence of a sunny day break, the storm-induced break is more predictable. Therefore, this study proposes a simple yet effective macro-based EWS for Earth-Filled Dam-Break Cases using a macro approach based on the Evacuation Clearance Time (ECT). By comparing the ECT value with the arrival time of the floods from the affected areas, additional evacuation time can be obtained, which will be used to determine the EWS. The proposed EWS for Cengklik Dam is given in three levels of warning indicated by the reservoir water level at +141.36 m, +141.40 m, and +141.45 m. With the proposed EWS, the results show that 100% of people are expected to reach the evacuation point safely. The case study shows that the proposed EWS can significantly reduce the risk impact of the dam-break events.

In this research, a numerical investigation was carried out on the effect of obstacle presence on the water flow during the dam-break in a dry bed. The validity of the numerical simulations was confirmed after comparing the results with the experimental evidence. Rectangular, trapezoidal and triangle obstacles were simulated numerically to explain the obstacle effect on the water flow. Water surface tracking and turbulent flow were modeled using the Volume of Fluid (VOF) method and the standard k-ω model, respectively. Pressure and velocity variations during the dam-break flow are presented and analyzed. HIGHLIGHTS Simulation of dam-break flow.; Presence of an obstacle in the flow.; Different obstacle geometries.; Numerical verification of water surface.; Pressure distributions during flow after dam-break.;

[Display omitted] • More particles are needed to capture more accurate dynamics since the flow undergoes breaking at its interface. • The velocity vector particle at the corner is shorter than the velocity vector of particles in the middle of the channel. • The particles in the bend corner move only around the corner, cause a stagnation point, and increase the bend pressure. • The density of the liquid also has a significant impact on the pressure distribution along the channel wall. Using a core catcher in the nuclear reactor is a tremendous idea to minimize the risk when the core of the reactor experiences melting conditions. In developing the core catcher design, the behavior of the corium is essential to understand. Therefore, an investigation of the behavior of melted UO 2 is necessary. In this study, the behavior of melted UO 2 flowing in a 90° bend channel was simulated by using the Moving Particle Semi-Implicit method. Important variables such as surface level, velocity, flow rate, pressure distribution, the Reynolds number, and the Froude number have been determined by analyzing open channel flow. The obtained results indicated that the simulation positively agrees with the experiment. By simulation, for fresh water case, the surface levels are 0.02–0.0885 m, the magnitudes of velocities are 0.04–2.94 m/s, flow rates are 0.00033–0.05 m3/s, the pressure distributions are 0–3000 Pa, the Reynolds numbers are 0.0349×105–5.07×105, and the Froude numbers are 0.0367–3.7095. For UO 2 case, the surface levels are 0.0239–0.1144 m, the magnitudes of velocities are 0.02–3.36 m/s, flow rates are 0.0000624–0.0538 m3/s, the pressure distributions are 0–11380 Pa, the Reynolds numbers are 0.102×105–9.93×105, and the Froude numbers are 0.049–2.687. The obtained results indicated that, in isothermal case, when the cooling effect are neglected, the flow of UO 2 inside the 90° bend is similar to those of fresh water for gravity-inertia regime in high Reynolds numbers. The flow rates of all liquids were in pillows regime. In addition, mass accumulation at the bend causes a stagnation point at the bend and increases the pressure on the bend wall. Additionally, the density of the liquid plays a significant influence in the pressure distribution. Moreover, when the Reynolds number is high and the flow is typically turbulent, the Froude number becomes a more significant indicator of flow characteristics. The material strength of the bend against pressure is an essential factor that needs to be considered carefully in reactor construction. [ABSTRACT FROM AUTHOR]

Following Antuono (2010), a frictional shock wave model with an improved seaward boundary condition (ISBC) was developed to simulate the bore-driven swash hydrodynamics in this study. It is found that bottom friction has a negligible effect when the shock wave propagates towards the original shoreline, whereas it plays important roles in the area near the swash tip and during the backwash. The ISBC increases the swash water depth and the onshore flow velocity, whereas it decreases the flow velocity during the backwash stage, thus the bottom friction effect. A comparison between the present shock wave model and the dam-break model was conducted, which indicates that these two models present similar swash hydrodynamics if the traditional seaward boundary condition is applied, whereas modifications of the water depth and flow velocity under different ISBCs are less significant for the present shock wave model compared to the dam-break model. Swash excursion increases with the ISBC in the shock wave model, which however keeps uniform in the dam-break model. Subsequently, model validation was conducted with respect to the experimental data of Kikkert et al. (2012). Comparing with the dam-break model result, swash hydrodynamics (water depth and flow velocity) in the uprush and early backwash stages could be better reproduced by the present shock wave model. • A shock wave solution with an improved seaward boundary condition (ISBC) was derived for the frictional swash process. • Effects of the bottom friction and the ISBC were quantitatively specified using the present shock wave solution. • Comparison between the shock wave and dam-break models was conducted. • The present shock wave model reproduces the measured swash hydrodynamics better than the dam-break model. [ABSTRACT FROM AUTHOR]

This study proposes a numerical model for depth-averaged Reynolds equations (shallow-water equations) to investigate a dam-break problem, based upon a two-dimensional (2D) second-order upwind cell-centre finite volume method. The transportation terms were modelled using a modified approximate HLLC Riemann solver with the first-order accuracy. The proposed 2D model was assessed and validated through experimental data and analytical solutions for several dam-break cases on a wet and dry bed. The results showed that the error values of the model are lower than those of existing numerical methods at different points. Our findings also revealed that the dimensionless error parameters decrease as the wave propagates downstream. In general, the new model can model the dam-break problem and captures the shock wave superbly.

In this paper, the theoretical framework is a depth-integrated two-phase model capable of considering many essential physical aspects such as reproducing the propagation of debris flows with soil permeability ranging from high to low and considering the pore-water pressure evolution. In this model, the pore fluid is described by an additional set of depth-integrated balance equations in order to take into account the velocity of pore fluid. The model employs a frictional rheological law for the granular material, and the interstitial fluid is treated as a Newtonian fluid. A drag law describes the interaction between interstitial fluid and grains. The variables of permeability, porosity, and drag force are included in the governing equations to consider the interaction between the phases. This paper aims to extend a generalized two-phase depth-integrated model to enhance the description of the interaction between the two phases and their respective movements. It allows us to increase our understanding of the mechanism behind natural rapid landslides. To evaluate the developed approach, a set of dam-break problems has been performed. These simulations provide interesting information in simple and controlled situations on the landslide propagations with different degrees of soil permeability and the interaction between solid and fluid phases. The extended model has also been applied to simulate the dynamics of the Acheron rock avalanche, which is an appropriate benchmark to examine the applicability of the model to real cases. [ABSTRACT FROM AUTHOR]

A laser profilometry technique was upgraded to detect underwater bed level evolution with a laser and a single camera for highly transient laboratory experiments. The proposed procedure is simple, but achieves a similar performance as that met by more complex and expensive methods. This technique was applied to a dam-break test case over a mobile bed in a channel with a 90° bend, for which water and bed levels were both continuously recorded at five different places. Photogrammetry was then used to reconstruct the final topography, whose main features could be explained by analysing only a few appropriately chosen linear bed profiles. This cheap, simple, flexible and accurate method thus proves to be an interesting alternative to more complex methods for morphodynamics investigations in the case of fast transient flows. [ABSTRACT FROM AUTHOR]

The complex nature of debris flows suggests that the pore-water pressure evolution and dewatering of a flowing mass caused by the high permeability of soil or terrain could play an essential role in the dynamics behavior of fast landslides. Dewatering causes desaturation, reducing the pore-water pressure and improving the shear strength of liquefied soils. A new approach to landslide propagation modeling considering the dewatering of a mass debris flow has drawn research attention. The problem is characterized by a transition from saturated to unsaturated soil. This paper aims to address this scientific gap. A depth-integrated model was developed to analyze the dewatering of landslides, in which, desaturation plays an important role in the dynamics behavior of the propagation. This study adopted an SPH numerical method to model landslide propagation consisting of pore-water and a soil skeleton in fully or partially saturated soils. In a two-phase model, the soil–water mixture was discretized and represented by two sets of SPH nodes carrying all field variables, such as velocity, displacement, and basal pore-water pressure. The pore-water was described by an additional set of balance equations to take into account its velocity. In the developed two-layer model, an upper desaturated layer and a lower saturated layer were considered to enhance the description of dewatering. This is the so-called two-phase two-layer formulation, which is capable of simulating the entire process of landslides propagation, including the large deformation of soils and corresponding pore-water pressure evolutions, where the effect of the dewatering in saturated soils is also taken into account. A dam-break problem was analyzed through the new and previously developed model. A flume test performed at Trondheim was also used to validate the proposed model by comparing the numerical results with measurements obtained from the experiment. Finally, the model was applied to simulate a real case lahar, which is an appropriate benchmark case used to examine the applicability of the developed model. The simulation results demonstrated that taking into account the effects of dewatering and the vital parameter of relative height is essential for the landslide propagation modeling of a desaturated flowing mass. [ABSTRACT FROM AUTHOR]

This paper presents the numerical simulations of flow and dam body sediment transport over a movable bed due to an earthfill dam break. The RANS equations, together with the k-ω SST turbulent model, are employed. The phase characteristic parameter is used as the phases of air, water, sediment, and bulk of dam body. The system of equations is solved numerically using the PISO algorithm. The numerical model is first verified using the dam break experimental data from the literature. The model successfully captures the temporal changes in the measured flow depths, pressures, wave fronts, and arrival times. The ve rified mod el is the n app lied to simulate the flow and sediment transport as a result of an artificial earthfill dam break having an obstacle at its downstream section. The simulations show that there is a noticeable decrease in the shock pressures at all points around the obstacle and there is an increase in the water levels. The bulk dam body sediment moves together with the water flow while spreading. It takes longer time for the sediment laden flow to reach the obstacle. The investigation of dam body formed by different soils shows that the soil type has minor effect while the transport of sediment can raise the water levels and change the morphology of the downstream section. [ABSTRACT FROM AUTHOR]

Baraj yıkılmasının meydana gelmesi durumunda özellikle barajın mansap bölgesinde oluşacak mal ve can kaybının en aza indirgenmesi ve barajın planlama aşamasında gerekli önlemlerin alınması için, baraj yıkılmasının sayısal modelleme teknikleriyle analiz edilmesi önemlidir. Ayrıca, mevcut barajların yayılım dalgasının mansap bölgesine olan etkisinin farklı senaryolarla analizi de bu yöntemler kullanılarak gerçekleştirilebilmektedir. Bu çalışmada, baraj mansabında herhangi bir yapı veya akım bulunmaması durumunda (kuru yatak) gerçekleşen baraj yıkılmasının sayısal modellemesi, sonlu hacimler yöntemiyle ANSYS- Fluent paket programı kullanılarak yapılmıştır. Sayısal modellemelerde baraj yıkılması yayılım dalgası akımını idare eden temel denklemlerin çözümünde, Re-normalization Grup k-ɛ (RNG), Kayma Gerilmesi Taşınım (Shear Stress Transport -SST) ve Ayrılmış Girdap Benzetim (Detached Eddy Simulation- DES) modelleri, su hava ara kesitinin belirlenmesinde ise akışkan hacimleri yöntemi (Volume of Fluid-VOF) kullanılmıştır. Farklı zamanlarda elde edilen deneysel ve sayısal su yüzü profillerinin karşılaştırılmasından, DES modelinin kullanılan diğer modellere kıyasla nispeten daha başarılı olduğu belirlenmiştir. Çalışma sonucunda, baraj yıkılması durumunda barajların mansap bölgesinin güvenlik önlemlerinin ve risk sınırlarının belirlenmesinde, sayısal modellemelerin güvenle kullanılabileceği görülmüştür.

Dam-break flow is known as one of the most horrible phenomena. Some hypothetical reservoir geometries were evaluated in literature, but in nature, each reservoir has a unique geometry. In the present research, dam-break flow was studied based on different reservoir geometries using FLOW-3D. Six reservoirs were considered: reservoirs R1 and R2 belonged to Mahabad Dam (Iran) and Tignes Dam (France), with asymmetric reservoirs, respectively; reservoirs R3 and R4 had symmetrical trapezoidal reservoirs with angles 30 and 45 degrees, respectively; reservoir R5 had a rectangular shape, extending from one side; and reservoir R6 had a long reservoir, which also was used to verify FLOW-3D. The model performance was verified by experimental results and FLUENT model in literature. Results showed FLOW-3D with mesh sizes 30×30×30 mm and k-ɛ turbulence model outperformed FLUENT, based on R2, RMSE, and MAE. The results of water levels and flow velocities at five points proved that dam-break flow could vary from one dam to another, considering reservoir geometry. Peak water levels and velocities have been measured to show how reservoir geometry could cause catastrophic flow.

Among others, dam-break waves are a common representation for tsunami waves near- or on-shore as well as for large storm waves riding on top of storm surge water levels at coasts. These extreme hydrodynamic events are a frequent cause of destruction and losses along coastlines worldwide. Within this study, dam-break waves are propagated over a composite bathymetry, consisting of a linear slope and an adjacent horizontal plane. The wave propagation on the slope as well as its subsequent inundation of the horizontal hinterland is investigated, by varying an extensive set of parameters, for the first time. To that end, a numerical multi-phase computational fluid dynamics model is calibrated against large-scale physical flume tests. The model is used to systematically alter the parameters governing the hydrodynamics and to link them with the physical processes observed. The parameters governing the flow are the slope length, the height of the horizontal plane with respect to the ocean bottom elevation, and the initial impoundment depth of the dam-break. It is found that the overland flow features are governed by the non-dimensional height of the horizontal plane. Empirical equations are presented to predict the features of the overland flow, such as flow depth and velocities along the horizontal plane, as a function of the aforementioned parameters. In addition, analytical considerations concerning these dam-break flow features are presented, highlighting the changing hydrodynamics over space and time and rising attention to this phenomenon to be considered in future experimental tests.

In this paper, we propose four different numerical methods for solving the Non-Linear Shallow Water Equations (NSWE), which are used to study dam-break flow over an obstacle. The discrete equations are formulated by applying various finite difference methods with filter involving wet-dry procedure. To validate our numerical model, several benchmark tests are carried out. Comparison of the computed results with the analytical and experiment data shows that our numerical model reproduces the flow with high accuracy. Moreover, we examine the effect of the shape and dimensions of the obstacle on downstream water height. Rectangular obstacles reduce downstream water height more significantly than triangular and trapezoidal ones. Downstream water height decreases non-linearly as obstacle height and width are increased.

Check dam systems are extensively utilized on the Loess Plateau. However, the development of the check dam system is restrained due to the failure hazard. To investigate the failure process of the check dam system and the corresponding effect, a hydrodynamic simulation was conducted in this study based on the failure of a typical check dam system, which occurred on 15 July 2012. The simulation was regarded as satisfactory based on verification with observed data of the peak discharge at the outlet of the catchment (NSE = 0.61, R2 = 0.83), breaches of damaged check dams (relative error < 20%) and maximum water depths in the front of 2 check dams (relative error of − 13.4% and + 4%). The simulation results indicated that the series failure in the tributary ditch did not cause the stack of peak discharges, and the peak flood discharge at the outlet of the catchment in this failure increased 20% compared to the status without dam-break and decreased 87% compared to the status without check dam. [ABSTRACT FROM AUTHOR]

This study presents a detailed analysis of the mechanics of scour around a square structure due to an inland-propagating tsunami-like bore using physical modeling. A series of hydraulic bores was simulated using the dam-break method in a flume at the University of Ottawa Hydraulics Laboratory. The dam-break bore was generated by releasing water from an impoundment through a rapidly opening swing gate. A novel video-recording system was used to record the evolution of the scour and vortex structure around the structure; image processing allowed tracking of the time and spatial evolution of the scour around the structure. In addition, different characteristics of a generated bore, final scour topography, and the relationship between scour depth and bore characteristics are assessed. The test program was designed such that propagation over the dry bed, typical of the first tsunami-induced inundation, was investigated. It was found that the high velocity and relatively short duration of a tsunami-like bore can induce rapid scour around the structure. The deeper bore depth over dry bed conditions resulted in faster rates of infiltration and scour. Furthermore, it was found that the longer duration of a turbulent bore induced more scour depth compared to that produced by a height-equivalent solitary or long wave. [ABSTRACT FROM AUTHOR]

Infrastructure, including roads, bridges, and municipal facilities, act as barriers to the downstream propagation of flood waves following a dam failure. The aim of this work is to investigate the effects of the obstacles and their arrangement on the evolution of flood waves during a dam breach using a numerical approach. The obstacles were arranged in two arrangements (triangular and inverted triangular) perpendicular to the flow direction in the downstream channel. Wave propagation during dam failure and flow dynamics were modelled by the finite volume method (FVM) using a CFD package. The evolution of the free surface of the dam breach was traced using the volume of fluid (VOF) method. However, the uncertainty of the model was evaluated using a sensitivity analysis with respect to the mesh resolution and turbulence models. The turbulence characteristics were captured by large-eddy simulations (LES) after validating the model using experimental data from the literature. The results show that the model can efficiently reproduce the wave development during a dam failure and the flow characteristics. The arrangement of the obstructions played an important role in the development of flow around the obstructions through the downstream channel. In this direction, the transitional flow regime, resultant forces in reservoir, and three-dimensional flow velocity around the obstaclees were predicted for different arrangements. [ABSTRACT FROM AUTHOR]

We investigate the Riemann Problem for a shallow water model with porosity and terrain data. Based on recent results on the local existence, we build the solution in the large settings (the magnitude of the jump in the initial data is not supposed to be “small enough”). One di culty for the extended solution arises from the double degeneracy of the hyperbolic system describing the model. Another di culty is given by the fact that the construction of the solution assumes solving an equation which has no global solution. Finally, we present some cases to illustrate the existence and non-existence of the solution.

Dam break analysis plays a key role in hydraulics engineering for safety. In this paper, 3D numerical simulations of dam-break flow using Finite Volume and Lattice Boltzmann methods are studied and discussed. All the computation in this work is achieved by ANSYS Fluent and XFlow. Large Eddy Simulation (LES) is employed as the turbulence model and the free surface flow is captured using a Volume of Fluid (VOF) model in the two simulation approaches. Results are then compared with experimental data on dam-break flow through complex obstacles. This experimental data is obtained by a high-speed camera aiming to capture free surface waves. The comparison between the experimental data and simulations shows good tendency. However, LBM requires less computational time.

In the current study, the treatment of air/water interface has been made on dam-break induced tsunami-like wave by the Coupled Level Set and Volume of Fluid (CLSVOF) three-dimensional modelling. The overall CLSVOF method adopts a Tangent of Hy-perbola for INterface Capturing (THINC) scheme with the Weighted Linear Interface Calculation (WLIC) and Level Set (LS) function for capturing interface and calculating normal vector, respectively. As far as THINC/WLIC scheme is concerned, since the convection problem of the VOF function can be solved well, the numerical diffusion can be avoided. The spatial terms in the LS equation were discretized by the Optimized Compact Reconstruction Weighted Essentially Non-Oscillatory (OCRWENO) scheme with fourth-order accuracy, which can avoid false oscillation of LS solution. By combining CLSVOF method with Immersed Boundary (IB) method, the simulation of dam-break induced tsunami-like wave impacting on a stationary breakwater can be carried out. Grid sensitivity, mass error and free-surface profile are first calculated for the tsunami-like wave problem to validate the proposed numerical algorithm, which shows excellent agreement between the numerical results and experimental data. Tsunami-like waves with varied tailgater levels are then investigated. Calculations of velocity magnitude, free-surface profile and wave elevation of the tsunami-like wave are conducted to investigate its dynamics and kinematics. [ABSTRACT FROM AUTHOR]

Solutions for dam-break flow mainly developed for rectangular channels are not applicable to prediction of the propagation of the dam-break wave in frictional triangular channels. This study presents an approximate solution considering the frictional effect on the dam-break flow in a dry horizontal triangular channel. Wave tip velocity is solved by an implicit formula for the product of time and resistance coefficients. All other hydraulic properties in the wave tip region can be expressed as explicit functions of wave tip velocity. Meanwhile, laboratory experiments have been performed for obtaining water surface profiles of dam-break flow from which the position and velocity of the wave tip front have been derived. Results show that retardation of the wave front position is more significant with the increases in both resistance and time. The proposed analytical solution shows satisfactory agreement with measurements, and clarifies how the behavior of the dam-break wave tip is affected by channel geometry. [ABSTRACT FROM AUTHOR]

Dam-break flow is known as one of the most horrible phenomena. Some hypothetical reservoir geometries were evaluated in literature, but in nature, each reservoir has a unique geometry. In the present research, dam-break flow was studied based on different reservoir geometries using FLOW-3D. Six reservoirs were considered: reservoirs R1 and R2 belonged to Mahabad Dam (Iran) and Tignes Dam (France), with asymmetric reservoirs, respectively; reservoirs R3 and R4 had symmetrical trapezoidal reservoirs with angles 30 and 45 degrees, respectively; reservoir R5 had a rectangular shape, extending from one side; and reservoir R6 had a long reservoir, which also was used to verify FLOW-3D. The model performance was verified by experimental results and FLUENT model in literature. Results showed FLOW-3D with mesh sizes 30x30x30 mm and k-ε turbulence model outperformed FLUENT, based on R2, RMSE, and MAE. The results of water levels and flow velocities at five points proved that dam-break flow could vary from one dam to another, considering reservoir geometry. Peak water levels and velocities have been measured to show how reservoir geometry could cause catastrophic flow. [ABSTRACT FROM AUTHOR]

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The complex nature of debris flows suggests that the pore-water pressure evolution and dewatering of a flowing mass caused by the high permeability of soil or terrain could play an essential role in the dynamics behavior of fast landslides. Dewatering causes desaturation, reducing the pore-water pressure and improving the shear strength of liquefied soils. A new approach to landslide propagation modeling considering the dewatering of a mass debris flow has drawn research attention. The problem is characterized by a transition from saturated to unsaturated soil. This paper aims to address this scientific gap. A depth-integrated model was developed to analyze the dewatering of landslides, in which, desaturation plays an important role in the dynamics behavior of the propagation. This study adopted an SPH numerical method to model landslide propagation consisting of pore-water and a soil skeleton in fully or partially saturated soils. In a two-phase model, the soil–water mixture was discretized and represented by two sets of SPH nodes carrying all field variables, such as velocity, displacement, and basal pore-water pressure. The pore-water was described by an additional set of balance equations to take into account its velocity. In the developed two-layer model, an upper desaturated layer and a lower saturated layer were considered to enhance the description of dewatering. This is the so-called two-phase two-layer formulation, which is capable of simulating the entire process of landslides propagation, including the large deformation of soils and corresponding pore-water pressure evolutions, where the effect of the dewatering in saturated soils is also taken into account. A dam-break problem was analyzed through the new and previously developed model. A flume test performed at Trondheim was also used to validate the proposed model by comparing the numerical results with measurements obtained from the experiment. Finally, the model was applied to simulate a real case lahar, which is an appropriate benchmark case used to examine the applicability of the developed model. The simulation results demonstrated that taking into account the effects of dewatering and the vital parameter of relative height is essential for the landslide propagation modeling of a desaturated flowing mass.

This data article presents a rich original experimental video sources and wide collections of laboratory data on water levels, sediment depths and wave front celerity values arose from different multiphase dam-break scenarios. The required data of dam-break shock waves in highly silted-up reservoirs with various initial up- and down-stream hydraulic conditions is obtained directly from high-quality videos. The multi-layer shock waves were recorded by three professional cameras mounted along the laboratory channel. The extracted video images were rigorously scrutinized, and the datasets were obtained through the images via image processing method. Different sediment depths in the upstream reservoir and dry- or wet-bed downstream conditions were considered as initial conditions, compromising a total of 32 different scenarios. A total of 198 original experimental videos are made available online in the public repository “Mendeley Data” in 8 groups based on 8 different initial upstream sediment depths [1–8]. 20 locations along the flume and 15 time snaps after the dam breaks were considered for data collecting. Consequently, a total of 18,000 water level and sediment depth data points were collected to prepare four datasets, which are uploaded in the public repository “Mendeley Data”. A total of 9600 water level data points could be accessed in [9,10], while 8400 sediment depth data points are available online in [11,12] and could be utilized for validation and practical purposes by other researchers. This data article is related to another research article entitled “Experimental study and numerical verification of silted-up dam-break” [13].

This paper gives a detailed description of the main hydrodynamic characteristics of different types of green water events occurring on a fixed structure in a series of experiments. High-speed video, at 250 fps, was used to capture the flow details from regular waves produced inside a wave flume. The green water events were classified according to their type and the results of the evaluation from the apparent and effective interaction features. The air cavities in the plunging-dam-break (PDB)-type events were almost spherical for longer waves. PDB with large, elliptical cavities, and hammer-fist (HF)-type events occurred with steeper waves. The highest wave front and bow run-up velocities were found in PDB and HF events, respectively. The size of the cavities in PDB events increases and becomes more elliptical for higher bow run-up velocities. The results of these experiments show that not all events can be treated in the same way as the dam-break (DB)-type events when designing structures or implementing models, as not all interactions with the deck happen when the shipping water crosses the bow edge. [ABSTRACT FROM AUTHOR]

Geophysical granular flows occur at the surface of the Earth and other planets with reduced atmospheric pressure. In this paper, we investigate the run-out of dam-break flows of particle-air mixtures with fine ( d = 75 μ m ) or coarse ( d = 150 μ m ) grains in a flume with different bottom roughness (δ ) and vacuum degrees ( P ∗ ). Our results reveal an increase of the flow run-out as d / δ decreases for fine d = 75 μ m -particles, and run-out decreases with the dimensionless ambient pressure ( P ∗ ) for a given d / δ . In contrast, the run-out for coarser d = 150 μ m -particles, is almost invariant respect to P ∗ and d / δ . These results show that autofluidization of fine-grained flows demonstrated by earlier works at ambient pressure also occurs at reduced pressure though being less efficient. Hence, autofluidization is a mechanism, among others, to explain long run-out of geophysical flows in different environments. [ABSTRACT FROM AUTHOR]

Dam-break flood waves represent a severe threat to people and properties located in downstream regions. Although dam failure has been among the main subjects investigated in academia, little effort has been made toward investigating wave propagation under the influence of tailwater depth. This work presents three-dimensional (3D) numerical simulations of laboratory experiments of dam-breaks with tailwater performed at the Laboratory of Hydraulics of Iskenderun Technical University, Turkey. The dam-break wave was generated by the instantaneous removal of a sluice gate positioned at the center of a transversal wall forming the reservoir. Specifically, in order to understand the influence of tailwater level on wave propagation, three tests were conducted under the conditions of dry and wet downstream bottom with two different tailwater depths, respectively. The present research analyzes the propagation of the positive and negative wave originated by the dam-break, as well as the wave reflection against the channel's downstream closed boundary. Digital image processing was used to track water surface patterns, and ultrasonic sensors were positioned at five different locations along the channel in order to obtain water stage hydrographs. Laboratory measurements were compared against the numerical results obtained through FLOW-3D commercial software, solving the 3D Reynolds-Averaged Navier–Stokes (RANS) with the k-ε turbulence model for closure, and Shallow Water Equations (SWEs). The comparison achieved a reasonable agreement with both numerical models, although the RANS showed in general, as expected, a better performance. [ABSTRACT FROM AUTHOR]