Dam-break Wave Research Articles

Data-driven reduced-order simulation of dam-break flows in a wetted channel with obstacles

Accurate and timely information on dam-break waves is essential for risk assessment and disaster mitigation. The unsteady flow interacting with in-channel obstacles renders numerical simulations computationally costly. This study establishes a machine learning (ML)-enhanced reduced-order model (ROM), which provides accelerated and accurate flow predictions. The model consists of three phases: dimensionality reduction, long short-term memory (LSTM) optimization and forecasting, and flow field reconstruction. The proper orthogonal decomposition (POD) first reduces the complexity of the physical system while maintaining the dominant flow dynamics. Subsequently, an LSTM fine-tuned by the grey wolf optimization (GWO) predicts the evolution of the POD coefficients in the reduced-order space. Lastly, the flow field is reconstructed using the high-energy POD modes and the estimated amplitudes. The proposed GWO-LSTM-ROM is evaluated for time-dependent dam-break flows in a wetted channel with obstacles. Based on the comparison of millions of data samples, the approach is highly consistent with the high-fidelity full-order model, with a coefficient of determination over 0.99. Meanwhile, the average computational efficiency is improved by 86%. The main contribution of this work is to develop an improved method for fast and accurate modeling of complex flows, benefiting a wide range of applications, e.g., multiphase flows and fluid-structure interactions.

TURBULENT BORES–INDUCED SCOUR AND PORE PRESSURE VARIATIONS AROUND A VERTICAL STRUCTURE

The scour due to the highly turbulent tsunami inundation is also a major threat to nearshore infrastructure [Nakamura, et al., 2008]. Research on local sediment erosion during tsunami events has shown a correlation between scour formation, pore pressure variations, and soil liquefaction [Mioduszewski and Maeno, 2003]. To understand the structures’ capacity to withstand the tsunami bores, it is critical to assess scour formation and pore pressure variations around their foundations [Macabuag et al., 2018, Nicholas et al., 2020; Mehrzad et at. 2021]. Young et al. (2008) conducted laboratory experiments to study tsunami induced liquefaction failure on a sand bed with two different slopes of 1V:5H and 1V:15H. The correlation between soil liquefaction and scour showed a direct link with bed slope and pore pressure and the peak pressure increased as the bed slope increased. Concerning the hydrodynamic forcing factor, research conducted by [Chanson, 2006] showed that the hydrodynamic characteristics of tsunami inundation can be adequately modeled using dam-break waves. The prime objective of this study was to comprehensively investigate the interaction of a wide range of hydrodynamic conditions and beach slopes on the variation of the pore pressure and associated scour.

Comparative analysis of numerical solutions of 2D unsteady dambreak waves using FVM and SPH method

Abstract This work presents a comparison of two-dimensional numerical solutions of unsteady free surface flow. This is a simulation of the dam-break wave with different configurations using based-mesh finite volume method and meshless smoothed particle hydrodynamics (SPH). Two well-known approaches, widely used in the computational fluid dynamics (CFD). These techniques have proven their robustness in the numerical treatment of such conservation laws. The main goal is to check the ability of the SPH method and the first order finite volume HLLC solver to reproduce the numerical solutions of the 2D shallow water equations. Based on many benchmark tests, one investigates the effect of the topographic variation along the x and y directions on behavior of the numerical solutions namely at the wet-dry front. The comparison between the simulated results, the analytical solutions and the experimental measurements shows a good correlation, although the finite volume approach remains more advantageous in terms of accuracy and the CPU time.

A numerical model for simulating the interaction of dam-break waves and floating structures

Using OpenFOAM, a numerical model is proposed to simulate the interaction of dam-break waves and floating structures. A geometric volume-of-fluid (VOF) method (isoAdvector) is combined with overset grid techniques. To avoid undesired air bubbles appearing in bulk water regions, a source term is introduced to the VOF equation. Attempts are made to alleviate mass conservation defects of the overset grid. It is found that: (i) Among the mesh interpolation schemes considered, the kernel scheme is the most preferable because it reaches a better balance between accuracy and efficiency; (ii) Extending donor cell stencils is not recommended because it magnifies the mass conservation defect of the overset grid; (iii) A strong coupling strategy is recommended because it alleviates the “water leak” phenomenon. Then, to validate the numerical model, two cases are simulated. The first case is a three-dimensional floating body case. The result demonstrates that this model performs better in terms of mass conservation than the model proposed by Wang et al. (2021). The second case is a two-dimensional experiment of the interaction of a dam-break wave and a floating box. The result demonstrates that this model has better temporal and spatial convergence than the default overset grid solver in OpenFOAM.

Historical comparison of the damage caused by the propagation of a dam break wave in a pre-alpine valley

Study regionValle Camonica basin and Lake Iseo in the Italian pre-alpine and alpine region. Study focusThis paper provides the first hydraulic reconstruction of the terminal part of the Gleno dam break with the propagation of the flood wave along a wide pre-alpine valley. The reconstruction of this part of the event, accomplished with a new 2D Shallow Water Equations solver, provides the occasion to tackle some important issues related to the computation of flood damage, a topic of paramount practical importance for which there is no widely accepted procedure in the literature. New hydrological insights for the regionThe hydraulic reconstruction provides insights into the propagation of the flood through the floodplain as far as the inlet of Lake Iseo. A methodology for damage computation is presented that considers a physically based criterion for the vulnerability of human life, with significant implications with respect to the use of simpler approaches based only on the density of the population. The economic evaluation of the damage to the built environment and to agricultural activities is included through a comprehensive recent approach. We discuss the variations of the expected damage due to the hydraulic works accomplished over the last 100 years to decrease the flood hazard, showing that its reduction has been followed by an increase in the expected damage in the surrounding areas.

A shock-capturing meshless method for solving the one-dimensional Saint-Venant equations on a highly variable topography

Abstract The Saint-Venant equations are numerically solved to simulate free surface flows in one dimension. A Riemann solver is needed to compute the numerical flux for capturing shocks and flow discontinuities occurring in flow situations such as hydraulic jump, dam-break wave propagation, or bore wave propagation. A Riemann solver that captures shocks and flow discontinuities is not yet reported to be implemented within the framework of a meshless method for solving the Saint-Venant equations. Therefore, a wide range of free surface flow problems cannot be simulated by the available meshless methods. In this study, a shock-capturing meshless method is proposed for simulating one-dimensional (1D) flows on a highly variable topography. The Harten–Lax–van Leer Riemann solver is used for computing the convective flux in the proposed meshless method. Spatial derivatives in the Saint-Venant equations and the reconstruction of conservative variables for flux terms are computed using a weighted least square approximation. The proposed method is tested for various numerically challenging problems and laboratory experiments on different flow regimes. The proposed highly accurate shock-capturing meshless method has the potential to be extended to solve the two-dimensional (2D) shallow water equations without any mesh requirements.

A consistent multi-resolution particle method for fluid-driven granular dynamics

Granular dynamics driven by fluid flow is ubiquitous in many industrial and natural processes, such as fluvial and coastal sediment transport. Yet, their complex multiphysics and multi-scale nature challenge numerical models’ accuracy and efficiency. Here, we develop a new multi-resolution mesh-free particle method, based on an enhanced weakly-compressible Moving Particle Semi-implicit (MPS) method, to study the dynamics of rapid fluid-driven granular erosion. We propose and validate a novel multi-resolution multiphase MPS formulation for the consistent and conservative form of the governing equations, including particle stabilization techniques. First, we discuss the numerical accuracy and convergence of the proposed approximation operators through two numerical benchmark cases: the multi-viscosity Poiseuille flow and the multi-density hydrostatic pressure. Then, coupling the developed model with a generalized rheology equation, we investigate the water dam-break waves over movable beds. The particle convergence study confirms that the proposed multi-resolution formulation predicts the analytical solutions with acceptable accuracy and order of convergence. Validating the multiphase granular flow reveals that the mechanical behavior of this fluid-driven problem is highly sensitive to the water-sediment density ratio; the bed with lighter grains experiences extreme erosion and interface deformations. For the bed with a heavier material but different geometrical setups, the surge speed, and the transport layer thickness remain almost identical (away from the gate). Furthermore, while the multi-resolution model accurately estimates the global sediment dynamics, the single-resolution model underestimates the flow evolution. Overall, the qualitative and quantitative analysis of results emphasizes the importance of multi-scale multi-density interactions in fluid-driven modeling.

A hybrid 1D-2D Lagrangian solver with moving coupling to simulate dam-break flow

In dam-break problems, two-dimensional (2D) models on the vertical plane appropriately capture the non-hydrostatic pressure distribution but with a high computational cost. This study presents a hybrid Lagrangian solver of one-dimensional (1D) shallow water flow and a 2D large-eddy simulation with a sub-particle scale to simulate dam-break flows over frictional beds. The proposed 1D-2D hybrid scheme is a useful trade-off between the accuracy of the 2D models on the vertical plane and the computational efficiency of 1D shallow water equations models. The configuration of sub-domains is established so that the 1D solves the regions with dominantly hydrostatic pressure, while the 2D solver accounts for the non-hydrostaticity. A moving coupling method is introduced based on two-layer shallow water equations with a uniform velocity distribution that constructs two sub-domains, including inner and outer zones in the section coupling model (SCM), or upper and lower layers within the layer coupling model (LCM). Then, the region with high vertical accelerations is substituted by the 2D model in the SCM or mixed SCM-LCM in which the overlapping zone and boundary interface move with time, based on the 1D flow feature. Also, a new method is proposed to deal with irregular boundary interfaces in the LCM while satisfying the momentum transfer. The present hybrid model is advantageous as it meets mass conservation, and there is no need for typical inflow/outflow boundary conditions at the coupling interfaces for simulating dam-break waves. Moving particle simulation (MPS) is utilized to solve the Lagrangian equations, which is advantageous in dealing with free-surface problems with large deformation. The model validation reveals that the hybrid results of water depths are in very good agreement with observed data and those obtained from the 2D model for selected dam-break flows with the ratio of initial depths downstream to upstream up to 0.4. In this respect, the average root-mean-square-error (RMSE) is computed at 8.09 mm in the SCM, 8.16 mm in the mixed SCM-LCM, and 7.48 mm in the pure 2D model, while both hybrid models save the computational time by 55% compared to the 2D model. Moreover, the mixed SCM-LCM preserves the nonlinearity of the wavefront over long times, whereas the SCM converts the wavefront into a shockwave considering the same number of fluid particles.

MPS-based simulation of dam-break wave propagation over wet beds with a sediment layer

In this study, a two-phase mesh-free method is employed to simulate the dam-break wave propagation along different wet bed conditions in the presence of sediment. The method is based on the mixture theory and volume fraction is incorporated for both water and sediments. The pressure Poisson equation is explicitly solved to obtain the pressure field for the water and the pressure field for the sediment is calculated by using the rheology model. The method is validated by simulating submerged granular column collapse and dam-break flow over a sediment layer. The method can reproduce the interface variation between water and sediment. The validated model is then used to simulate the dam-break wave propagation in the presence of both downstream water and sediment. Different dam-break waves induced by the upstream water depths are simulated and it is found that the dam-break wave can make the sediment move violently. The larger downstream water depth can slow down the sediment movements while the sediment movements are violent for shallower water downstream.

Study on the dynamic response of offshore bridge under earthquake action and tsunami impact

This paper takes an offshore continuous rigid bridge as the background bridge to reveal the dynamic response law of an offshore bridge under the action of earthquake and tsunami. A tsunami wave is simulated by a dam-break wave. A numerical model of a dam-break impact of a bridge pier is established in Fluent software, and k−ε turbulence model is chosen to solve the Navier–Stokes equation. Meanwhile, ABAQUS software is used to establish a three-dimensional nonlinear full bridge model. The dam-break wave working condition is proposed according to the Stoker theory. The bridge dynamic response index under a single earthquake action and a continuous earthquake tsunami action is calculated, and the dynamic response rules under the two actions are summarized. The results show that compared with the tsunami action alone, the sequential action of the earthquake and tsunami will cause a greater dynamic response of the bridge structure. With the increase in the height of the incoming tsunami wave, the waveform trend difference of the response index will be more significant. Moreover, the influence coefficient of the dynamic response index of the bridge tends to increase as the probability level of the earthquake occurrence decreases.

Numerical Study on Tsunami Force on Coastal Bridge Decks with Superelevation

Many coastal bridges have been destroyed or damaged by tsunami waves. Some studies have been conducted to investigate wave impact on bridge decks, but there is little concerning the effect of bridge superelevation. A three-dimensional (3D) dam break wave model based on OpenFOAM was developed to study tsunami-like wave impacts on bridge decks with superelevation. The Reynolds-averaged Navier–Stokes equations and the k-ɛ turbulence model were used. The numerical model was satisfactorily checked against Stoker’s analytical solution and the published hydrodynamic experiment. The validated model was employed to carry out parametric analyses to investigate the effects of upstream and downstream water depths and the bridge deck’s superelevation. The results show that the tsunami force is proportional to the relative wave height. The dam break wave impact on the bridge deck can be identified as two distinct scenarios according to whether the wave height is higher than the bridge deck top. The trend of the tsunami force is also different in different scenarios. The superelevation will significantly influence the tsunami forces acting on the box girder, with some exceptions.

Numerical Study of Tsunami Force on Superstructure of Offshore Rigid Frame Box Girder Bridge

Offshore bridges need to bear complex wave and current loads and face the threat of extreme loads such as tsunamis. Potential tsunamis will have disastrous effects on coastal areas. Compared with conventional beam bridges, there are few studies on rigid frame box girder bridges. In this paper, based on a continuous rigid frame box girder bridge in the offshore area, the parameters of tsunami impact force are analyzed. First, based on Stoke theory and water level in the storage area, the water level in the static water area and quasi stable area in the dam break wave working conditions are obtained, and 12 kinds of dam break wave working conditions are preliminarily proposed to be used for the background bridge. Then, according to the determined simulation working conditions, the box girder dam break impact numerical model is simulated. According to the calculated results, the stress characteristics of the box girder under the tsunami impact are described in the way of time history stage division, and on this basis, The stress mechanism is analyzed from the whole level and local level. The results show that on the whole level, the variation of horizontal force and vertical force with time can correspond to the variation of dam break flow around the box girder. At the local level, the horizontal wall boundary bears the vertical force, the vertical wall boundary bears the horizontal force, and the inclined wall boundary bears both the horizontal force and the vertical force. In addition, negative pressure is the cause of suction on the wall boundary. It provides a reference for the calculation and analysis of tsunami load of offshore rigid frame box girder bridges, the identification of bridge failure modes and the formulation of protective measures.

Influence of dam break scenarios on flood wave characteristics. Case study – Paltinu Dam, Romania

Among the various constructive types of dams, the arch dams breaches are the largest and the quickest to occur, leading to the most catastrophic flood waves. Therefore, prediction of the shape, magnitude and arrival time of the breach waves is of utmost importance for flood risk management. The study analyses in GIS environment the influence of different dam breach scenarios on the evolution in time and space of the flood wave. As a study case it was chosen the 108m in height, Paltinu arch-dam (Romania), built on Doftana River and its about 19km river reach down to the confluence with Prahova River. Several breach widths and depths are considered in the analysed scenarios, coupled with selected inflow hydrographs and initial reservoir water elevation, to assess their influence on the dam break wave characteristics and downstream flooded areas. To model the flood wave routing following the dam brake, HEC-RAS software is used. Inundation boundaries, characteristic depths and velocities, as well as arrival time in selected control sections are compared and conclusions are drawn.

Experimental investigation into the boundary layer structure near the tip of a dam-break wave on a dry, rough and horizontal bed

The boundary layer structure near the tip of dam-break waves, swash flow and tsunami, is important for understanding the shape and behavior of their tips and for sediment transport, which is observed under tips on mobile beds. In this study, the boundary layer structure near the dam-break tip on a dry, rough and horizontal bed was investigated experimentally. Horizontal velocities were obtained using advanced image processing techniques, and the concurrent bed shear stress was measured directly with a shear plate. The velocity structure is quantified in terms of the defect scale of horizontal velocity in the vertical direction δ defined by u(z)=u∞[1−e−zδ], while the asymptotic velocity u∞ is defined for each vertical so that the depth-averaged velocity equals the tip's speed of propagation. The experimental results indicate that the shape of the velocity profile changes rapidly with distance s from the contact point. The velocity profile is roughly linear very near the contact point corresponding to a rolling wheel or δ being much greater than the water depth. Further from the contact point, in our case, s/ks≳0.42, where ks is bed roughness, δ is only a fraction of the depth, and this fraction becomes constant, ca. 0.21, at distances greater than s/ks ≈ 1.67. Boundary layer growth as δ(s)∝s is in good agreement with the measured velocity profiles for s/ks ≳ 4. The concurrently measured bed shear stress after its peak can be well predicted with the proposed relationship δ(s)∝s.

Numerical Simulation of a Dam-Break Wave from Hydraulic Project No. 10 on the White Sea-Baltic Canal

Numerical Simulation of a Dam-Break Wave from Hydraulic Project No. 10 on the White Sea-Baltic Canal

Theoretical investigation of dam-break waves in frictional channels with power-law sections

Both the hydraulic resistance and the channel cross-sectional geometry have significant effect on the propagation of the dam-break waves. Analytical models including either of them have been available. However, it is not feasible to assess the comprehensive influence using the existing solutions. The present study considers a resistance-dominated wave tip region followed by an ideal fluid flow region in a dry horizontal channel whose cross-sectional shape is controlled by a power-law index n. Laboratory experiments and numerical simulations are conducted to measure/predict the water surface profiles of the dam-break flows in five types of flumes. The water depth, location and celerities of the wave front predicted by the analytical model agree well with the experimental and numerical results. The quantitative effects of the bottom resistance and the channel cross-sectional shape on the wave properties are investigated. Results show that the spatio-temporal variation in the wave feature of the dam-break flows strongly depends on the channel cross-sectional geometry; while the retardation effect of the bottom resistance becomes more significant as n increases. Furthermore, the derived analytic solution as well as the experimental data can be used for evaluating numerical solutions considering the hydraulic resistance and cross-sectional geometry.

Experimental study on hydrodynamic interaction between dam-break waves and circular pier

This paper focuses on the hydrodynamic interaction between dam-break waves and circular pier. Firstly, a series of dam-break waves under dry-bed and wet-bed conditions were conducted, the evolution of wave front profiles are obtained experimentally. Then, experimental studies on hydrodynamic interaction between these dam-break waves and a circular pier were carried out systematically. After that, the pressures and their vertical distributions on the front, back and lateral side of the circular pier are obtained and analyzed in detail. In which, sudden rise of pressures on the front side, obviously oscillatory pressures on the back side, and negative pressures on the lateral side are observed. Furthermore, the forces and moments on the circular pier are presented, and their characteristics are explored. Among which, the maximum force and moment occur in the impulse stage when there are fluctuations upstream of the wave front, otherwise they occur in the quasi-stationary stage. In addition, the corresponding dimensionless coefficients are obtained and their evolutions are revealed elaborately. Finally, the calculation formulas for maximum force and moment on circular pier, considering the variation of wave front profile, are proposed, and related coefficients are suggested. This study could provide reference for the improvement of calculation method.

An experimental study on hydrodynamic process, beach profile, and sand migration in swash zone under action of dam-break bore

This study makes an experimental study on hydrodynamics and sediment driven by dam-break waves in swash zones of three sandy beaches. The experiment adopts three beaches: a 1:10 uniform-sand beach, a 1:10 non-uniform-sand beach, and a 1:35 non-uniform-sand beach. This paper reports its measurements on swash water depth, morphology, bedload, and migration of sand particles. It also analyzes the hydraulic jump and sandbar, sorting and sedimentology characteristics, and fractal dimension of bedform. The analysis indicates that the uniformness of sand particle sizes plays an important role in hydrodynamic behaviors, bedform evolution, bedload transport, and migration of sand particles. The fractal dimension of beach profiles lies between 1.15 and 1.25 after swash action, despite changes in bed profiles.

Experimental and Numerical Investigation of Beach Slope Effects on the Hydrodynamic Loading of Tsunami-like Surges on a Vertical Wall

Over the past decades, hydraulic surge generated by dam-break waves has been used to simulate the effects of tsunamis on coastal infrastructure. This study investigates the slope effects on hydrodynamic loading of dam-break waves on structure when propagating over four different inclined beds (0-, 5-, 10-, 15-degree) by experiment and numerical simulation using OpenFOAM and DualSPHysics. Except for small discrepancies in the pressure time-history, numerical results obtained with both OpenFOAM and DualSPHysics agreed closely with the experimental dynamic pressures. The results revealed that the hydrodynamic pressure decreased after an initial impact peak from the lowest transducers in the 5-, 10-, and 15-degree cases when compared with the horizontal case. However, the dynamic pressure of transducers at same corresponding level increased with an increase in the slope. The integrated experimental hydrodynamic forces were similar to the numerical results for the 0- and 5-degree cases, while they were higher for the 10- and 15-degree cases due to insufficient pressure data. By investigating the relation between the force decrease and slopes, a non-dimensional reduction factor was proposed from the linear fitness for slope effects estimation. This experimental and numerical study can provide novel insight on the hydrodynamic force calculation of tsunami-like surges on coastal infrastructures when considering beach slope.

Numerical Simulations on the Flooding into a Damaged Cabin with a Flexible Bulkhead Based on the Mixed-Mode Function-Modified MPS Method

Floodwater entering the damaged cabin and impacting the bulkhead can cause damage to the watertight compartment and affect the survival of the ship. The elastic deformation of the bulkhead can slow down the impact and affect the flow field, which affects the hydrodynamic distribution inside the cabin. In this work, numerical simulations on the flooding phenomena into the damaged cabin with various stiffness, watertight bulkheads are carried out by using the mixed-mode function-modified moving particle semi-implicit (MPS) method, with the objective of investigating the influence of the stiffness of the watertight bulkheads on the structural impact load. Firstly, the numerical model based on the MPS method is set up to predict the dam-break wave impact load on an elastic plate and compared with the experimental measurements to verify the feasibility of the method. Then, the evolution of the flooding process of the damaged cabin with four different stiffnesses are simulated and the impact pressure on the bulkhead is predicted and compared. It is found that the flexible watertight bulkheads not only can reduce the peak pressure acting on it, but also have an effect on the hydrodynamic pressure distribution of the entire cabin. This implies that properly selected stiffness and material properties of watertight bulkheads can mitigate the impact of flooding on the damaged cabin’s bulkheads.