Dam-break Wave Research Articles

Comparative Analysis of Hydrodynamic Loads on Bridge Piers: Assessing Standards through Numerical Modeling

Currently, there is an alarming difference in the estimated actions on piers resulting from flash-floods and tsunamis as prescribed by international Structural Design Codes. Previous studies have explored the interaction between surge waves and piers from a fluid-dynamics perspective, but there is no assessment about the relevance of the methods used in Structural Design to determine the hydrodynamic pressure resultants. To determine the degree of conservatism embedded in design, results from the different approaches are compared against validated numerical simulations. Three-dimensional numerical analyses were conducted using the OpenFOAM platform, employing the Large Eddy Simulation turbulence modeling approach to simulate the dam-break wave impacting the pier. The findings revealed that the maximum force was not necessarily caused by the stream’s first strike and could be sustained over time. The hydrodynamic pressure center consistently occurred at two-thirds of the stream depth, significantly impacting the overturning moments experienced by the pier. Identified inconsistencies between Codes underscore the need for revision of non-conservative approaches in predicting the design forces.

Hydrodynamic optimization and performance verification of fairings for round-ended cofferdams using dam-break wave experiments and numerical simulations

Round-ended cofferdams are crucial for large-scale marine projects but are vulnerable to the complex marine environment, including waves, tides, and storms. Enhancing the hydrodynamic performance of these cofferdams is essential for improving safety and efficiency in marine construction. This study introduces a novel fairing design aimed at reducing water flow resistance during the quasi-stable stage of a tsunami. The flow field is analyzed using computational fluid dynamics (CFD) simulations, and an adaptive surrogate model is employed to optimize the parameterized fairing shape. The results demonstrate that the optimized shape significantly suppresses vortex shedding, leading to a 16.59 % reduction in the drag coefficient and a 44.3 % reduction in the lift coefficient under flow conditions. Experimental and numerical simulations of dam-break waves are conducted for two designs, R1 and R0. By comparing their flow field and force characteristics, it is found that R1 effectively separates waves during the impulse stage, reduces wave climb height, and decreases impact loads. In the quasi-stable stage, R1 mitigates the blockage effect, reducing the liquid level difference between the front and back, and thus lowering flow forces. Experimental data further reveals that when the downstream is a dry riverbed, R1′s load reduction is particularly notable, with maximum reductions of 45.62 % in the impulse stage and 28.75 % in the quasi-stable stage. When the riverbed is wet, the maximum load reduction rates are 18.04 % and 8.72 %, respectively. Therefore, R1 not only reduces the resistance of round-end cofferdams under water currents but also under extreme wave forces, providing valuable insights for advancing ocean engineering design.

Dam-Break waves over mobile bed

Dam-break waves are a major concern for communities and infrastructures in flood-prone areas. The impact of dam-break waves against rigid obstacles after propagation on a mobile bed is lacking both in experimental datasets and in numerical investigations aimed at assessing the capabilities and limitations of available morphodynamic models. To fill these gaps, a novel data set from experiments of dam-break waves propagating over an erodible bottom and impacting over a vertical wall is presented and compared with numerical simulations performed by the Saint Venant–Exner model. First, the effects of bottom mobility are discussed by comparison with the corresponding fixed bed condition. Then, supplementary conditions are investigated for different initial water levels and reservoir lengths. The comparison with the results of the numerical simulation shows that the relatively simple model employed is able to reproduce the general features of the process and the peak impact force with reasonable accuracy.

Numerical investigation on the evolutionary characteristics of landslide dam-break flow in a wet-bed channel with riparian vegetation

Riparian vegetation always grows on both sides of a natural river during a dam-break event, while the river typically retains some water instead of completely drying out. The RNG k-ϵ turbulence model is employed to examine the evolutionary characteristics of the dam-break flow in the downstream vegetated channel. This model facilitates the analysis of water-level fluctuations, velocity distributions, and the retardation effects of vegetation on the dam-break flow by varying the initial water depth (IWD) in the downstream channel. Results indicates that as the water depth in the downstream channel increases, the dam-break wave tends to form more readily, possesses a larger amplitude, and the duration of rapid congestion in the dam-break current decreases. Hence, the surface velocity gradually declines and shows an intermittent distribution. Vegetation impedes the flow evolution in the vegetated area, an effect that diminishes progressively with increasing IWD. In contrast, vegetation hastens the evolution of water flow in the main channel, which remains minimally affected by the IWD.

Experimental study of dam-break-like tsunami loads on vertical structures with overhanging horizontal slabs: Slab with air chamber

Tsunamis pose a significant threat to coastal engineering. A comprehensive physical experiment was conducted to examine the effect of air chambers on vertical structures with overhanging horizontal slabs under tsunami bores. This paper, serving as the second part of the series, contrasts with conditions without air chambers (flat slab as Part I) to underscore the chamber's effects. The experiment employed dam-break waves to simulate tsunamis, and the collected pressure data and experimental images were analyzed. Results show that the chambers restrict water flow, thereby enhancing the impact on the slab. This focusing effect greatly increases both maximum uplift and horizontal pressure (by almost 1.3 times). The uplift pressure rises with increasing chamber volume, while horizontal pressure escalates with greater beam volume. However, both pressures diminish as slab height increases. Water flowing into the chambers disperses air, generating numerous bubbles that accumulate above, forming an air layer that reduces pressure signal fluctuations. This phenomenon of entrained and trapped air is compared and analyzed with existing literature. The maximum pressure of the nearshore air chamber is greater than that of the offshore air chamber by 13% (3.68 kPa vs. 3.27 kPa), while the quasi-steady pressures of the two are almost equal. Differences in pressure between chambers result from the sequence of water flow impacts and reflections. New design envelope equations and conversion coefficients are proposed based on experimental data. The focusing coefficient, considering bore height, slab height, and chamber parameters, is summarized. Novel equations for estimating pressure on a flat slab with specific chambers are proposed, with validation results indicating high accuracy.

Enhancing tsunami resilience for coastal bridge piers through seawall-integrated breakwaters: An experimental study

In ocean engineering, breakwater plays a crucial role in protecting coastal structures such as bridge pier from the impact of extreme sea waves. However, enhancing the existing breakwaters' ability to withstand extreme wave remains an urgent issue to address. This study explores the reinforcement strategy of breakwater against extreme sea waves by installing seawalls on the breakwater. Utilizing dam-break wave generation techniques to simulate tsunamis, the study experimentally evaluates the effectiveness of seawalls in reducing the tsunami forces exerted on bridge pier model and numerically investigates the tsunami forces on the seawalls. The focus of this research is to analyze the pressure distribution on seawalls and the impact of different seawall configurations on the reduction of tsunami forces on bridge pier model. Results show that: Under the tested wave condition (a) The height of the seawall on the breakwater is a critical parameter, as increasing wall height reduces the tsunami forces exerted on the bridge pier behind it. The taller seawalls are subjected to greater tsunami forces in tested cases; (b) The trend of extreme pressure values for different seawalls starts increasing at the bottom and then decreases; (c) There is a critical distance that the breakwater being most effective at reducing tsunami impact forces between the bridge pier model and the breakwater. This study not only deepens the understanding of the interaction between tsunami waves and seawalls but also offers practical guidance for designing structures with disaster resilience, significantly influencing the future design and construction of tsunami-resistant coastal infrastructure.

Large eddy simulation of power-law fluid dam break wave impacting against a vertical wall

Large eddy simulation of power-law fluid dam break wave impacting against a vertical wall

Experimental study on the influence of water depth and bed slope variations on dam-break flood wave propagation

Damage to dam structures frequently results in catastrophic consequences. Consequently, understanding of the characteristics of the movement of dam-break flow along the sloping wet bed can assist in the issuance of timely flood warnings and risk mitigation. In this study, a series of large-scale flume experiments was conducted with the objective of investigating the effects of upstream and downstream water depth and bed slope on the propagation of dam-break waves. The water level is measured and processed to calculate the wavefront velocity. Results show that the wave propagation behavior can be classified as bore and undular waves through the global Froude numbers (Frx) and local Froude numbers (Frl). When Frx < 1.225 or Frl < 1.475, the dam-break wave propagates as the undular wave. In the undular wave state, the wavefront velocity (U) decreases with increasing water depth ratio α. Additionally, the U with Frx shows a similar trend, where the experimental value surpasses the analytical solution. The dimensionless maximum wave height (ΔHmax) increases with Frx and then decreases. The deviation from the analytical solution ranges between 67.22% and 127.38%. When Frx > 1.225 or Frl > 1.475, the dam-break wave propagates as the bore wave. In the bore wave state, the U increases slightly with the water depth ratio α, while the change rule of U with Frx is similar to it. The dimensionless maximum wave height (ΔHmax) remains relatively constant as Frx increases, showing a high degree of consistency with the analytical solution. The presence of bed slope results in increased wavefront velocity and wave heights, while an increase in α results in the emergence of more pronounced undular wave phenomena. Furthermore, the experimental results are compared with existing analytical solutions, and the validity of the analytical solutions and their limitations are discussed.

Experimental study on wavefront flow characteristics of dam-break wave at initial stage on wet bed

The flow characteristics of dam-break wave in the initial stage of downstream wet bed are studied experimentally by digital image measurement technologies. First, the fine wavefront structure and its velocity were captured by the optical flow method, and an image measurement technology of water level based on edge detection was proposed. Then, the comparison and verification were carried out using the numerical simulation. The mean error is −7.369%, −1.243%, and 1.317% under depth ratio (σ) is 0.2, 0.25, and 0.33, and the error of most cases is within ±15% except σ = 0.2. The results show that large eddy simulation combined with volume of fluid method could accurately predict the distribution of dam-break water level, but it tends to overestimate the propagation velocity of the wavefront by about 10.3%. In addition, Stoker's quasi-steady paradigm has been proven to accurately predict the mean and steady-state flow characteristics of dam-break wave. Furthermore, the wavefront structure of the initial stage was subdivided into three sub-stages, namely, the jump stage, the transition stage, and the stable stage. Following that, the flow characteristics of each stage under the condition of the σ = 0.25 were studied in detail. The results show that the morphology of the wavefront structure is driven by the transformation of its internal energy in the initial stage. In summary, the work reveals the flow characteristics and quantitative flow results of the initial stage of dam-break wave under the wet river bed, thus improving the accuracy of dam-break accident prediction.

Partial dam-break wave characteristics due to partial gate opening

Understanding how to predict the characteristic height of a dam-break wave is crucial for effective risk management in dam-break scenarios. This study introduces an experimental framework to simulate partial dam-break waves triggered by partial gate openings. We conducted numerous experiments to explore how different factors, including water-level differences (hi), reservoir widths (L), dam-break openings (e), and submerged depths (hw) influence the characteristic heights of the main-wave peak (h1c), subwave peak (h2c), and main-wave trough (h1t). Our analysis led to the development of an equation for predicting h1c. Furthermore, we compared the partial dam-break wave profile with the theoretical profile of a solitary wave, identifying optimal conditions for solitary wave generation and examining the velocity characteristics of partial dam-break waves. The results reveal that: (1) h1c, h2c, and h1t have positive correlations with hi and L, but negative correlations with e and hw; (2) notably, the main-wave pre-peak profile aligns more closely with the solitary wave theory; and (3) the solitary wave theory accurately predicts the main-wave peak velocity. This study enhances our understanding of wave characteristic evolution during partial dam-breaks and can be used for validation in numerical simulations.

A modified weakly compressible smoothed particle hydrodynamics mixture model for accurate simulation of wave and porous structure interaction

In this study, a modified weakly compressible smoothed particle hydrodynamics (WCSPH) mixture model was developed to more accurately simulate the interaction between waves and porous structures. In this model, we enhanced the governing equations of the traditional WCSPH mixture model by introducing Darcy velocity, apparent density, and an adjustable smoothing length. This refinement ensures that the modified model effectively maintains the conservation of fluid volume in seepage simulations. Additionally, this paper proposes a permeable interface treatment technique that replaces traditional smoothed particle hydrodynamics interpolation with finite element shape function interpolation, significantly enhancing computational efficiency. At the same time, we also introduced and revised a particle shifting technique, which further increases the computational precision of the model. The modified WCSPH mixture model was then applied to simulate several physical experiments, including the dam-break wave propagation in a permeable dam, the attenuation of solitary waves on a permeable riverbed, the propagation of the solitary wave on a submerged porous structure, and the breaking process of waves passing through permeable breakwaters. Through comparison with the experimental data and other numerical results, the current model was comprehensively verified from various aspects, such as fluid volume conservation, wave evolution in and around the porous structure, and pressure distribution characteristics. The results confirm the excellent performance of the current model in simulating the interaction between waves and porous structures.

Experimental investigations of propagation characteristics and wave energy of dam-break waves on wet bed

Understanding the characteristics of dam-break flows that move along a sloping wet bed is essential for timely flood warnings and risk mitigation. This study conducts laboratory experiments in a sizable flume, encompassing various upstream and downstream water depths and bed slopes. It examines the effects of the ratio between upstream and downstream water depths and the slope of the flume on the dam-break wave height and the velocity of the wavefront. The findings revealed that the average relative error between theoretical and experimental values initially decreases and increases as the slope rises. The dam-break waveform is characterized by introducing a global Froude number Frx and a local Froude number Frl, with critical values of Frx=1.225 and Frl=1.475. In addition, a model for predicting the dam-break wave height is developed by linearly fitting the values between dimensionless wave height and the local Froude number, and it is validated by comparison to experimental data. Based on experimental data and the Stoker equation, an attenuation function for the dam-break wave height at a downstream location is proposed for the undular wave. Finally, a theoretical analysis is conducted to predict the energy of the first dam-break wave.

Numerical investigation of dam break flow over erodible beds with diverse substrate level variations

Abstract This study aimed to comprehensively investigate the influence of substrate level difference and material composition on dam break wave evolution over two different erodible beds. Utilizing the Volume of Fluid (VOF) method, we tracked free surface advection and reproduced wave evolution using experimental data from the literature. For model validation, a comprehensive sensitivity analysis encompassed mesh resolution, turbulence simulation methods, and bed load transport equations. The implementation of Large Eddy Simulation (LES), non-equilibrium sediment flux, and van Rijn’s (1984) bed load formula yielded higher accuracy compared to alternative approaches. The findings emphasize the significant effect of substrate level difference and material composition on dam break morphodynamic characteristics. Decreasing substrate level disparity led to reduced flow velocity, wavefront progression, free surface height, substrate erosion, and other pertinent parameters. Initial air entrapment proved substantial at the wavefront, illustrating pronounced air-water interaction along the bottom interface. The Shields parameter experienced a one-third reduction as substrate level difference quadrupled, with the highest near-bed concentration observed at the wavefront. This research provides fresh insights into the complex interplay of factors governing dam break wave propagation and morphological changes, advancing our comprehension of this intricate phenomenon.

Experimentos de ruptura de barragens de terra homogêneas por galgamento

ABSTRACT This work physically simulates the effect of low and high flow rates and filling times of reservoirs and rupture due to overtopping (caused by intense rains) of small homogeneous silty-sand earthfill dams. The experiments seek to verify how input variations impact the formation of the breach and the rupture wave. The results show that different filling times, soil moisture and composition, and degree of compaction affect landfill saturation, failure time, and breach formation. The result confirms that smaller breaches with a higher degree of compaction led to a lower peak rupture flow compared to dams with low degree of compaction. The rupture hydrograph presents a faster descent stage than an exponential hydrograph. Simulations and models based on this law may minimize the effect of the dam-break wave, also impacting water resource decision-making for damage reduction. The results were extrapolated to a real prototype, providing information and a database for the studies of overtopping dam-break waves.

Analysis of Dam Break Wave Using Analytical, Computational Fluid Dynamics, and Experimental Approaches

This research aims to examine the capability of the Computational Fluid Dynamics (CFD) method in simulating the behavior of dam break waves. It begins by building a 2D numerical simulation using OpenFOAM. To overcome the influence of turbulence, we employed the Large Eddy Simulation (LES) turbulent model, specifically the k-Equation and Smagorinsky model. The simulation was developed by applying the Navier-Stokes equations using the finite volume method in OpenFOAM. The analysis focuses on the free surface of a dam break. The results are in good accordance with both analytical and experimental results. The simulation has followed the trend of experimental and analytical free surface profiles at the dam break’s early and late conditions. The low mesh number on the computational domain caused significant differences in the wavefront of the dam break. It reduced the accuracy of the calculation between the water and air interface. This study highlights the importance of understanding dam break wave behavior as part of risk mitigation for dam leakage. The behavior of dam break waves can be observed by determining observation positions at different locations, with the water gate of a dam serving as the reference point. These highly accurate numerical results indicate that the CFD approach employing OpenFOAM can be relatively cost-effective yet accurate in analyzing multiphase problems, such as dam breaks. This CFD approach is expected to contribute to developing mitigation and disaster prevention in the future.

Analysis of Dam Break Wave Using Analytical, Computational Fluid Dynamics, and Experimental Approaches

This research aims to examine the capability of the Computational Fluid Dynamics (CFD) method in simulating the behavior of dam break waves. It begins by building a 2D numerical simulation using OpenFOAM. To overcome the influence of turbulence, we employed the Large Eddy Simulation (LES) turbulent model, specifically the k-Equation and Smagorinsky model. The simulation was developed by applying the Navier-Stokes equations using the finite volume method in OpenFOAM. The analysis focuses on the free surface of a dam break. The results are in good accordance with both analytical and experimental results. The simulation has followed the trend of experimental and analytical free surface profiles at the dam break’s early and late conditions. The low mesh number on the computational domain caused significant differences in the wavefront of the dam break. It reduced the accuracy of the calculation between the water and air interface. This study highlights the importance of understanding dam break wave behavior as part of risk mitigation for dam leakage. The behavior of dam break waves can be observed by determining observation positions at different locations, with the water gate of a dam serving as the reference point. These highly accurate numerical results indicate that the CFD approach employing OpenFOAM can be relatively cost-effective yet accurate in analyzing multiphase problems, such as dam breaks. This CFD approach is expected to contribute to developing mitigation and disaster prevention in the future.

Discussion of “Experimental investigation into the boundary layer structure near the tip of a dam-break wave on a dry, rough and horizontal bed” by Beibei Xu, Rui Shi, Peter Nielsen, Zheng Gong

Discussion of “Experimental investigation into the boundary layer structure near the tip of a dam-break wave on a dry, rough and horizontal bed” by Beibei Xu, Rui Shi, Peter Nielsen, Zheng Gong

Assessing the impact of an arch-dam breach magnitude and reservoir inflow on flood maps

Abstract Different scenarios of an arch-dam breach and their impact on the time-space evolution of flood waves are analysed using numerical modelling. As the accidents involving this type of dam are among the most catastrophic ones, the 108 m in height Paltinu arch-dam, Romania, was chosen as a case study due to its problems in the past. Three dam breach magnitudes and two inflow hydrographs for the worst-case scenario of Normal Operating Pool elevation in the reservoir were chosen as variable parameters, to assess their influence on the dam break wave characteristics and downstream flooded areas. The flood was routed along the 18 km reach of the Doftana River down to the confluence with the Prahova River. A 2D numerical model was set up with the help of HEC-RAS software, which was also used to analyse the resulting hazard maps under a GIS environment. Comparison of inundation boundary, maximum depths and velocities, as well as the arrival time at control sections allow for conclusions to be drawn. These predictive results of shape, magnitude, and time to peak of the flood waves are essential for flood risk management to obtain the risk maps, estimated damage costs, and possible affected areas.

Instabilities of a dam-break wave of power-law fluids

The paper theoretically investigates the stability properties of the dam-break wave of a fluid with power-law rheology. Assuming the long-wave approximation, a depth-averaged flow model is considered. The linear stability analysis of the wave is carried out to individuate the marginal stability conditions. To this aim, the multiple-scale technique is applied with reference to the kinematic wave solution, which formally limits the validity of the theoretical achievements to relatively long time scales. Both shear-thinning and shear-thickening fluids are considered. Similarly to the case with uniform conditions, the analysis indicates that stable conditions can be associated with a marginal value of the Froude number. However, differently from the uniform conditions, the marginal Froude number is shown to be a function not only of the power-law index but also of the streamwise gradient of the base flow velocity and of the disturbance wavelength. The critical Froude number is found to be larger than the corresponding one in uniform conditions. Numerical solutions of the full model confirmed the outcomes of the linear stability analysis for both shear-thinning and shear-thickening fluids.

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.