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Profiles of (a) flow depth, (b) average velocity and (c) discharge for Channel I obtained from the analytical solution.
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Cross-sectional channel shape is a primary factor influencing dam-break floods. However, it is difficult to analytically understand the impact of the cross-sectional shape on flood wave propagation because most of the existing analytical solutions are only applicable to channels with specific cross-sections (e.g., rectangular, parabolic and triangu...
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Context 1
... flow depth, average velocity, discharge profiles along the length of the channel at t = 0.5 s, 1.0 s, 1.5 s and 2.0 s for Channel I are shown in Fig. 5. The top profiles at a given time correspond to the downward slope (S 0 = 0.02), the bottom profiles are related to the upward slope (S 0 = À0.02), and the middle profiles are related to the horizontal channel. The effect of the bed slope on the flow depth becomes more prominent as time increases. It is interesting that the flow depth, ...
Context 2
... depth, average velocity, discharge at the dam site (x = 0) for different times is fixed (h ⁄ = 0.554, u ⁄ = 0.624, and Q ⁄ = 0.481) for the horizontal channel (S 0 = 0) and varies with time for the sloping channel (S 0 -0). The flow depth at the dam site is larger than 0.554 for the downward slope and is smaller than 0.554 for the upward slope. Fig. 5(b) implies that the dam-break flood is promoted on the downward-sloping channel and is retarded on the upward-sloping channel. The velocity profiles become mild over time. The average velocity at the dam site is greater than 0.624 for the downward slope and less than 0.624 for the upward slope. It can be seen from Fig. 5(c) that discharge ...
Context 3
... for the upward slope. Fig. 5(b) implies that the dam-break flood is promoted on the downward-sloping channel and is retarded on the upward-sloping channel. The velocity profiles become mild over time. The average velocity at the dam site is greater than 0.624 for the downward slope and less than 0.624 for the upward slope. It can be seen from Fig. 5(c) that discharge on the downward-sloping channel is increased due to the promotion of a dam-break flood, whereas the discharge on the upward-sloping channel is decreased due to the flood retardation. The discharge at the dam site is greater than 0.481 for the downward slope and is less than 0.481 for the upward ...
Context 4
... Fig. 5(c) shows that the location of the maximum discharge along the downward-sloping channel (S 0 > 0) is on the upstream side of the dam and is farther from the dam with increasing time. The opposite case occurs for the upward-sloping channel (S 0 < 0). The maximum discharge along the horizontal channel (S 0 = 0) occurs exactly at the dam ...
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Citations
... The analytical solutions discussed thus far have been derived under the assumptions of shallow water and long waves, which overlook vertical velocities and accelerations and assume pressure to be hydrostatic (Yang et al., 2022). Wang et al. (2017) proposed an analytical solution for a dry sloping bed with an arbitrary cross-sectional shape by employing the separation of the cross-sectional shape parameter and the method of characteristics. This technique was subsequently applied to develop an analytical solution for the shallow-water equations on a wet sloping bed (Wang et al., 2020b). ...
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 〖Fr〗_x and a local Froude number 〖Fr〗_l, with critical values of 〖Fr〗_x=1.225 and 〖Fr〗_l=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.
... Although dam breaks have led to considerable theoretical research, many existing analyses and studies have been performed using rectangular channels [7,8]; consequently, the general understanding between the cross-sectional shape and the fluid dynamics remains limited. Other cross-sectional shape models have also been developed [9][10][11][12], but these models are only applicable to trapezoidal, parabolic, and triangular cross-sections. ...
... Other cross-sectional shape models have also been developed [9][10][11][12], but these models are only applicable to trapezoidal, parabolic, and triangular cross-sections. Considering the complexity of a natural river, the analytical solution is not applicable to all channel shapes [7]. Notably, most models cannot simulate channels considering the influence of friction, which is ignored in the derivation process. ...
... Although the trend-smoothing method provides satisfactory longitudinal continuity for river terrain, the lateral characteristics of the river terrain are not considered, and rectangular channels are assumed. However, the analytical understanding of flood wave propagation in rectangular channels following dam failures remains limited [7]. Overall, even under conditions with the same depth and width, the cross-sectional area of different river channel shapes can vary greatly (Fig. 1). ...
Flood forecasts commonly require reliable input data to accurately reflect the actual situation. Although widely used in the world, the coarse digital elevation models (DEMs) from remote sensing often provide poor representations of the real topography due to the effects of water and mountain shadows. Remote sensing methods cannot reliably capture riverbed elevations, and fine-scale DEMs are needed. Due to the high cost of labor and material resource limitations, complete fine-scale DEMs are difficult to obtain to support flood forecasting across long reaches at sufficiently high precision. This work presents a refined three-dimensional river channel reconstruction method by considering the longitudinal and lateral topographic features of rivers to provide realistic river terrain data. The performance of this method in flood simulation is confirmed by simulating extreme flood events in the lower-670-km reach of the Jinsha River at a 30-m resolution. The numerical simulations and field measurements are quantitatively compared in terms of flood peaks and flood propagation processes. Numerical experiments further confirm that uncertainties from terrain inputs are not amplified by the hydrodynamic model when producing the final flood forecasting outputs.
... Aureli et al. (2014) presented a semi-analytical method for predicting the dam-break flow rate hydrograph by generalizing an analytical solution for the dam-break problem in a rectangular frictionless sloping channel to a valley with a power-law section flow in order to consider the most common river channel shapes of natural valleys. Wang et al. (2017) also adopted the treatment for the channel cross section given by Wu et al. (1993) to develop an analytical solution of the dam-break flood wave propagation in a dry sloped channel with an irregular-shaped cross-section. They also identified the limitations of the cross-section treatment. ...
... His study focused mainly on the vertical change of flow velocity and he did not have an overall grasp of the water flow in the whole basin. Wang et al. (2017) deduced the analytical solution in dry sloped bed under arbitrary cross-sectional shape by using the method of cross-sectional shape parameter separation. Lin et al. (1980) applied characteristic theory and Riemann method to obtain the dam-breaking wave solutions for different cross sections in flat bottom. ...
There has been little study on the impact of bottom slope on dam break wave propagating along a triangular wet channel. In this study, laboratory experiments are conducted in a large-scale triangular laboratory flume, covering a range of bed slope and rations of upstream over downstream water depth. Water surface and stage hydrograph wave height are collected using the non-intrusive measurement methods, which are used to obtain wave characteristics. Results show that for dry bed, the wavefront celerity increases with the increase of the slope; while for a wet bed, the wavefront celerity decreases as the slope increases and the decrease rate is significantly reduced. Moreover, the wavefront celerity decreases with the increase of water depth ratio. The maximum wave height at each measurement location decreases with the increase of water depth ratio. According to the arrival of the maximum wave height, the dam-break wave can be classified into two modes, namely Type A in which wave height gradually rises to the maximum when flow reaches and Type B in which the maximum wave height appears at the beginning of the dam failure. This study is useful for in-depth understanding of the dam-break wave evolution in sloping triangular wet rivers.
... The flow torrentiality is due to the change in the slope of the river on the whole part (I b ). Indeed, the flow velocity increases rapidly in the wave tip zone, where the flow resistance dominates [67,68]. High-velocity peaks represent steep slopes, where flow speed recorded the highest velocity at the level of the breach formation (Vmax = 38.57 ...
... This analysis can provide a reasonable approximation of the impacts of a flood wave on areas located downstream in the event of dam failure. Thus, this information is essential for flood hazard classification and developing emergency action plans [68]. ...
The risk related to embankment dam breaches needs to be evaluated in order to prepare emergency action plans. The physical and hydrodynamic parameters of the flood wave generated from the dam failure event correspond to various breach parameters, such as width, slope, and formation time. This study aimed to simulate the dam breach failure scenario of the Yabous dam (northeast Algeria) and analyze its influence on the related areas (urban and natural environments) downstream of the dam. The simulation was completed using the sensitivity analysis method to assess the impact of breach parameters and flooding on the dam break scenario. The flood wave propagation associated with the dam break was simulated using the one-dimensional HEC-RAS hydraulic model. This study applied a sensitivity analysis of three breach parameters (slope, width, and formation time) on five sites selected downstream of the embankment dam. The simulation showed that the maximum flow of the flood wave recorded at the level of the breach was 8768 m3/s, which gradually attenuated along the river course to reach 1972.7 m3/s at about 8.5 km downstream the dam. This study established the map of flood risk areas that illustrated zones threatened by the flooding wave triggered by the dam failure due to extreme rainfall events. The sensitivity analysis showed that flood wave flow, height, and width revealed positive and similar changes for the increases in adjustments (±25% and ±50%) of breach width and slope in the five sites. However, flood wave parameters of breach formation time showed significant trends that changed in the opposite direction compared to breach slope and width. Meanwhile, the adjustments (±25% and ±50%) of the flood hydrograph did not significantly influence the flood parameters downstream of the dam. In the present study, the HEC-RAS 1-D modeling demonstrated effectiveness in simulating the propagation of flood waves downstream of the dam in the event of dam failure and highlighted the impact of the breach parameters and the flood hydrographical pattern on flood wave parameters.
... The flow torrentiality is due to the change in the slope of the river on the whole part (Ib). Indeed, the flow velocity increases rapidly in the wave tip zone, where the flow resistance dominates [46,47]. High velocity peaks represent steep slopes, where flow speed recorded the highest velocity at the level of the breach formation (Vmax=38.57 ...
... This analysis can provide a reasonable approximation of the impacts of flood wave on areas located downstream in the event of dam failure. Thus, this information is essential for flood hazard classification and developing emergency action plans [47]. ...
The risk related to embankment dam breaches needs to be evaluated in order to prepare emergency action plans. The physical and hydrodynamic parameters of the flood wave generated from dam-failure event correspond to various breach parameters such as width, slope and formation time. This study aimed to simulate dam-breach failure scenario of Yabous dam (NE Algeria) and analyze its influence on areas (urban and natural environments) downstream the dam. The simulation was completed using the sensitivity analysis method in order to assess the impact of breach parameters on the dam-break scenario. The propagation of flood wave associated to dam-break was simulated using the one-dimensional HEC-RAS hydraulic model. This study ap-plied a sensitivity analysis of three breach parameters (slope, width, and formation time) in five sites selected downstream the embankment dam. The simulation showed that the maximum flow of the flood wave recorded at the level of the breach was 8768 m3/s, which gradually attenuated along the river course to reach 1579.2m3/s at about 8.5km downstream the dam. This study estab-lished the map of flood-prone areas that illustrated zones threatened with the flooding wave trig-gered by the dam failure due to extreme rainfall events. The sensitivity analysis showed that flood wave flow, height and width revealed positive and similar changes for the increase in adjustments (±25% and ±50%) of breach width and slope in the 5 sites. However, flood wave parameters of breach formation time showed significant trends that changed in the opposite direction compared to breach slope and width.
... It can be seen that most of the above studies were carried out under the condition of either the horizontal bed or the slopping dry bed, and the focus of the previous studies were mainly on the macroscopic characteristics of the flow. However, the actual dam break flows or Favre waves are affected by both the bed slope and the tailwater (Wang et al., 2017;Wang et al., 2020b). The internal movement information (such as, velocity profile and bed shear stress distribution) is not only important for assessing the potential channel erosion damage (Shigematsu et al., 2004), but also a significant parameter for understanding and mitigating the impact of dam-break flood and Favre waves (Biscarini et al., 2010). ...
The bed slope and the tailwater depth are two important ones among the factors that affect the propagation of the dam-break flood and Favre waves. Most previous studies have only focused on the macroscopic characteristics of the dam-break flows or Favre waves under the condition of horizontal bed, rather than the internal movement characteristics in sloped channel. The present study applies two numerical models, namely, large eddy simulation (LES) and shallow water equations (SWEs) models embedded in the CFD software package FLOW-3D to analyze the internal movement characteristics of the dam-break flows and Favre waves, such as water level, the velocity distribution, the fluid particles acceleration and the bed shear stress, under the different bed slopes and water depth ratios. The results under the conditions considered in this study show that there is a flow state transition in the flow evolution for the steep bed slope even in water depth ratio α = 0.1 (α is the ratio of the tailwater depth to the reservoir water depth). The flow state transition shows that the wavefront changes from a breaking state to undular. Such flow transition is not observed for the horizontal slope and mild bed slope. The existence of the Favre waves leads to a significant increase of the vertical velocity and the vertical acceleration. In this situation, the SWEs model has poor prediction. Analysis reveals that the variation of the maximum bed shear stress is affected by both the bed slope and tailwater depth. Under the same bed slope (e.g., S0 = 0.02), the maximum bed shear stress position develops downstream of the dam when α = 0.1, while it develops towards the end of the reservoir when α = 0.7. For the same water depth ratio (e.g., α = 0.7), the maximum bed shear stress position always locates within the reservoir at S0 = 0.02, while it appears in the downstream of the dam for S0 = 0 and 0.003 after the flow evolves for a while. The comparison between the numerical simulation and experimental measurements shows that the LES model can predict the internal movement characteristics with satisfactory accuracy. This study improves the understanding of the effect of both the bed slope and the tailwater depth on the internal movement characteristics of the dam-break flows and Favre waves, which also provides a valuable reference for determining the flood embankment height and designing the channel bed anti-scouring facility.
... Natural rivers are generally with sloped beds and irregular cross-sectional areas. Wang et al. (2017) state that a polyline cross-section can determine a natural river's complex shape. In this regard, they proposed an analytical solution for an inviscid dam-break problem over a dry sloped bed in a prismatic channel with SARKHOSH AND JIN 10.1029/2020WR028742 16 of 29 Figure 14. ...
... Finally, a solitary wave runup over an inclined beach is taken into account. (Wang et al., 2017) and LES model (Wang et al., 2017) for an inviscid dam-break over a dry sloped bed with an irregular crosssectional area at different time steps. LES, large eddy simulation; MPS, moving particle simulation; SWE, shallow-water equation. ...
... Finally, a solitary wave runup over an inclined beach is taken into account. (Wang et al., 2017) and LES model (Wang et al., 2017) for an inviscid dam-break over a dry sloped bed with an irregular crosssectional area at different time steps. LES, large eddy simulation; MPS, moving particle simulation; SWE, shallow-water equation. ...
Here, a moving particle simulation method is presented to spatially integrate the cross-sectional average shallow water equations using a prediction-correction procedure for the time discretization. A density-ratio equation is derived for the water depth computation according to the particle number density concept. The newly derived equation does not miscalculate the water depth in case an incorrect searching radius parameter is adopted, unlike the typical volume-summation formula in meshless shallow water flows. A new one-dimensional Spiky kernel function is developed to satisfy the unity condition employed in the Newton-Raphson iteration to calculate the water depth. Dynamic stabilization is adopted to capture shockwave problems, a case-independent technique based on the inelastic collision with unequal masses. The convective flux term is eliminated under the Lagrangian framework, and so the momentum is adequately conserved without the need for any special treatment. The proposed scheme maintains the exact C-property, meaning that the water depth gradient and bed slope are hydrostatically well balanced within a discretized solution domain. Compared to analytical solutions and experimental data, the results of this study reveal that the present model is a robust numerical solver without unphysical oscillations. It can capture various shock problems, including steep gradient shock-front, discontinuous wet bed, transcritical flow regimes, and irregular bed topography. The present model can also simulate the dry-wet flow transition influenced by friction without experiencing any divisions by zero, negative values, or unphysical perturbations. This advantage is basically due to the water particles' absence and presence for the dry and wet regions, respectively.
... Dam-break floods usually cause considerable economic and loss of life [1][2][3][4]. Due to its practical importance and difficulty for obtaining the field data, extensive studies on dam-break floods have been carried out using laboratory experiments, numerical simulation, and theoretical analysis [5][6][7][8][9][10]. The propagation of the dam-break wave is significantly affected by the cross-sectional shape of channels [7,11]. ...
... Due to its practical importance and difficulty for obtaining the field data, extensive studies on dam-break floods have been carried out using laboratory experiments, numerical simulation, and theoretical analysis [5][6][7][8][9][10]. The propagation of the dam-break wave is significantly affected by the cross-sectional shape of channels [7,11]. Wang et al. [12] conducted laboratory experiments to investigate the difference of dam-break wave evolution in both the rectangular and triangular channels. ...
A sudden dam failure is usually simulated by the rapid removal of a gate in laboratory tests and numerical simulations. The gate-opening time is often determined according to the Lauber and Hager instantaneous collapse criterion (referred to as the Lauber–Hager criterion), which is established for a rectangular open channel with a dry bed. However, this criterion is not suitable for non-rectangular channels or initial wet-bed conditions. In this study, the effect of the gate-opening time on the wave evolution is investigated by using the large eddy simulation (LES) model. The instantaneous dam-break, namely, a dam-break without a gate, is simulated for comparison. A gate-opening criterion for generating dam-break flow in a non-rectangular wet-bed channel is proposed in this study, which can be used as an extension of the Lauber–Hager criterion and provides a more comprehensive and reasonable estimate of the gate opening time.
... In his solution, the water depth in the wave-front region was affected by the selection of the surface roughness height k s . Wang et al. (2017) deduced the analytical solution of the dry sloped bed under arbitrary cross-sectional shape by using the method of cross-sectional shape parameter separation. Using different methods, various analytical solutions are also obtained (Fernandez-Feria, 2006;Mangeney et al. 2000;Wang and Pan, 2014). ...
