The initial stages of dam-break flow

1998 ◽  
Vol 374 ◽  
pp. 407-424 ◽  
Author(s):  
P. K. STANSBY ◽  
A. CHEGINI ◽  
T. C. D. BARNES
Keyword(s):  
Dam Break ◽  
Complex Flow ◽  
Jet Formation ◽  
Initial Release ◽  
Flow Interactions ◽  
Nonlinear Potential ◽  
Small Times ◽  
Dam Break Flow ◽  
Surface Profiles ◽  
Different Levels

Experiments have been undertaken to investigate dam-break flows where a thin plate separating water at different levels is withdrawn impulsively in a vertically upwards direction. Depth ratios of 0, 0.1 and 0.45 were investigated for two larger depth values of 10 cm and 36 cm. The resulting sequence of surface profiles is shown to satisfy approximately Froude scaling. For the dry-bed case a horizontal jet forms at small times and for the other cases a vertical, mushroom-like jet occurs, none of which have been observed previously. We analyse the initial-release problem in which the plate is instantaneously removed or dissolved. Although this shows singular behaviour, jet-like formations are predicted. Artificially smoothing out the singularity enables a fully nonlinear, potential-flow computation to follow the jet formation for small times. There is qualitative agreement between theory and experiment.In the experiments, after a bore has developed downstream as a result of highly complex flow interactions, the surface profiles agree remarkably well with exact solutions of the shallow-water equations which assume hydrostatic pressure and uniform velocity over depth.

The initial stages of dam-break flow

1998 ◽  
Vol 374 ◽  
pp. 407-424 ◽  
Author(s):  
P. K. STANSBY ◽  
A. CHEGINI ◽  
T. C. D. BARNES
Keyword(s):  
Dam Break ◽  
Complex Flow ◽  
Jet Formation ◽  
Initial Release ◽  
Flow Interactions ◽  
Nonlinear Potential ◽  
Small Times ◽  
Dam Break Flow ◽  
Surface Profiles ◽  
Different Levels

Experiments have been undertaken to investigate dam-break flows where a thin plate separating water at different levels is withdrawn impulsively in a vertically upwards direction. Depth ratios of 0, 0.1 and 0.45 were investigated for two larger depth values of 10 cm and 36 cm. The resulting sequence of surface profiles is shown to satisfy approximately Froude scaling. For the dry-bed case a horizontal jet forms at small times and for the other cases a vertical, mushroom-like jet occurs, none of which have been observed previously. We analyse the initial-release problem in which the plate is instantaneously removed or dissolved. Although this shows singular behaviour, jet-like formations are predicted. Artificially smoothing out the singularity enables a fully nonlinear, potential-flow computation to follow the jet formation for small times. There is qualitative agreement between theory and experiment.In the experiments, after a bore has developed downstream as a result of highly complex flow interactions, the surface profiles agree remarkably well with exact solutions of the shallow-water equations which assume hydrostatic pressure and uniform velocity over depth.

scholarly journals Experimental and Numerical Analysis of 3D Dam-Break Waves in an Enclosed Domain with a Single Oriented Obstacle

2020 ◽  
Vol 2 (1) ◽  
pp. 35
Author(s):  
Selahattin Kocaman ◽  
Stefania Evangelista ◽  
Giacomo Viccione ◽  
Hasan Güzel
Keyword(s):  
Three Dimensional ◽  
Dam Break ◽  
Small Scale ◽  
Complex Flow ◽  
Free Surfaces ◽  
Dam Break Flow ◽  
Computational Fluid Dynamics Cfd ◽  
Dam Breaking ◽  
3D Software ◽  
Downstream Area

Flood caused by a dam-breaking flow may be catastrophic for the downstream area due to the sudden discharge of large volumes of water. Besides the complex flow of the propagating dam-break wave, the presence of structures such as bridges and buildings yield free surfaces which can be accurately reproduced by means of three-dimensional Computational Fluid Dynamics (CFD) software. The prediction of the dam-break flow main features in the presence of obstacles has a crucial role in decreasing the damage. In this study, small-scale laboratory experiments were conducted to examine the problem with a single obstacle. Five ultrasonic sensors were used as measurement devices. Measurements were compared with the numerical results obtained with the FLOW-3D software, solving RANS equations with the k- turbulence closure model. A good agreement was observed.

Investigation of Dam-Break Flow Over Abruptly Contracting Channel With Trapezoidal-Shaped Lateral Obstacles

2012 ◽  
Vol 134 (8) ◽  
Author(s):  
Hatice Ozmen-Cagatay ◽  
Selahattin Kocaman
Keyword(s):  
Numerical Models ◽  
Rectangular Cross Section ◽  
Dam Break ◽  
Water Levels ◽  
Navier Stokes ◽  
Video Images ◽  
Dam Break Flow ◽  
Downstream Section ◽  
Surface Profiles ◽  
Good Agreement

The present paper aims to investigate the dam-break flow over dry channel with an abrupt contracting part in certain downstream section. A new experiment was carried out in a smooth-prismatic channel with rectangular cross section and horizontal bed. A digital imaging technique was adopted for flow measurement and thus flood wave propagation was sensitively obtained. Synchronous filmed images of the dam-break flow were nonintrusively acquired with three cameras, through glass sidewalls of the channel. Free surface profiles and time evolution of water levels were derived directly from the recorded video images using virtual wave probe without disturbing the flow. Furthermore, the present study highlights the formation and propagation of the negative bore due to abruptly contracting channel. The measured results were compared with the numerical solution of Reynolds averaged Navier–Stokes (RANS) equations with k-ε turbulence model and good agreement was achieved. New experimental data can be useful for scientific community to validate numerical models.

scholarly journals A Well-Balanced and Fully Coupled Noncapacity Model for Dam-Break Flooding

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Zhiyuan Yue ◽  
Huaihan Liu ◽  
Youwei Li ◽  
Peng Hu ◽  
Yanyan Zhang
Keyword(s):  
Sediment Transport ◽  
Momentum Conservation ◽  
Dam Break ◽  
Governing Equations ◽  
Complex Flow ◽  
Flow Phenomena ◽  
Dam Break Flow ◽  
Flow And Sediment Transport ◽  
Volume Method ◽  
Fully Coupled

The last two decades have seen great progress in mathematical modeling of fluvial processes and flooding in terms of either approximation of the physical processes or dealing with the numerical difficulties. Yet attention to simultaneously taking advancements of both aspects is rarely paid. Here a well-balanced and fully coupled noncapacity model is presented of dam-break flooding over erodible beds. The governing equations are based on the complete mass and momentum conservation laws, implying fully coupled interactions between the dam-break flow and sediment transport. A well-balanced Godunov-type finite volume method is used to solve the governing equations, facilitating satisfactory representation of the complex flow phenomena. The well-balanced property is attained by using the divergence form of matrix related to the static force for the bottom slope source term. Existing classical tests, including idealized dam-break flooding over irregular topography and experimental dam-break flooding with/without sediment transport, are numerically simulated, showing a satisfactory quantitative performance of this model.

scholarly journals Experimental and Numerical Analysis of a Dam-Break Flow through Different Contraction Geometries of the Channel

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 1124 ◽  
Author(s):  
Selahattin Kocaman ◽  
Hasan Güzel ◽  
Stefania Evangelista ◽  
Hatice Ozmen-Cagatay ◽  
Giacomo Viccione
Keyword(s):  
Wave Propagation ◽  
Numerical Models ◽  
Rectangular Channel ◽  
Dam Break ◽  
Water Levels ◽  
Experimental Results ◽  
Complex Flow ◽  
Related Field ◽  
Dam Break Flow ◽  
Irregular Topography

Dam-break wave propagation usually occurs over irregular topography, due for example to natural contraction-expansion of the river bed and to the presence of natural or artificial obstacles. Due to limited available dam-break real-case data, laboratory and numerical modeling studies are significant for understanding this type of complex flow problems. To contribute to the related field, a dam-break flow over a channel with a contracting reach was investigated experimentally and numerically. Laboratory tests were carried out in a smooth rectangular channel with a horizontal dry bed for three different lateral contraction geometries. A non-intrusive digital imaging technique was utilized to analyze the dam-break wave propagation. Free surface profiles and time variation of water levels in selected sections were obtained directly from three synchronized CCD video camera records through a virtual wave probe. The experimental results were compared against the numerical solution of VOF (Volume of Fluid)-based Shallow Water Equations (SWEs) and Reynolds-Averaged Navier-Stokes (RANS) equations with the k-ε turbulence model. Good agreements were obtained between computed and measured results. However, the RANS solution shows a better correspondence with the experimental results compared with the SWEs one. The presented new experimental data can be used to validate numerical models for the simulation of dam-break flows over irregular topography.

scholarly journals Stochastic Uncertainty in a Dam-Break Experiment with Varying Gate Speeds

2021 ◽  
Vol 9 (1) ◽  
pp. 67
Author(s):  
Hiroshi Takagi ◽  
Fumitaka Furukawa
Keyword(s):  
High Speed ◽  
Pressure Sensors ◽  
Dam Break ◽  
Maximum Pressure ◽  
Vertical Acceleration ◽  
Ship Wakes ◽  
Dam Break Flow ◽  
Statistical Relationships ◽  
Flow Propagation ◽  
Impulsive Pressure

Uncertainties inherent in gate-opening speeds are rarely studied in dam-break flow experiments due to the laborious experimental procedures required. For the stochastic analysis of these mechanisms, this study involved 290 flow tests performed in a dam-break flume via varying gate speeds between 0.20 and 2.50 m/s; four pressure sensors embedded in the flume bed recorded high-frequency bottom pressures. The obtained data were processed to determine the statistical relationships between gate speed and maximum pressure. The correlations between them were found to be particularly significant at the sensors nearest to the gate (Ch1) and farthest from the gate (Ch4), with a Pearson’s coefficient r of 0.671 and −0.524, respectively. The interquartile range (IQR) suggests that the statistical variability of maximum pressure is the largest at Ch1 and smallest at Ch4. When the gate is opened faster, a higher pressure with greater uncertainty occurs near the gate. However, both the pressure magnitude and the uncertainty decrease as the dam-break flow propagates downstream. The maximum pressure appears within long-period surge-pressure phases; however, instances considered as statistical outliers appear within short and impulsive pressure phases. A few unique phenomena, which could cause significant bottom pressure variability, were also identified through visual analyses using high-speed camera images. For example, an explosive water jet increases the vertical acceleration immediately after the gate is lifted, thereby retarding dam-break flow propagation. Owing to the existence of sidewalls, two edge waves were generated, which behaved similarly to ship wakes, causing a strong horizontal mixture of the water flow.

A three dimensional dam break flow: Small time behavior

2021 ◽  
Vol 110 ◽  
pp. 102583
Author(s):  
Elona Fetahu ◽  
Oguz Yilmaz
Keyword(s):  
Three Dimensional ◽  
Small Time ◽  
Dam Break ◽  
Time Behavior ◽  
Dam Break Flow

scholarly journals Investigate Impact Force of Dam-Break Flow against Structures by Both 2D and 3D Numerical Simulations

Water ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 344
Author(s):  
Le Thi Thu Hien ◽  
Nguyen Van Chien
Keyword(s):  
Impact Force ◽  
Numerical Models ◽  
Splitting Method ◽  
Dam Break ◽  
Navier Stokes ◽  
Dynamic Force ◽  
Exact Mass ◽  
Initial Water ◽  
Dam Break Flow ◽  
2D And 3D

The aim of this paper was to investigate the ability of some 2D and 3D numerical models to simulate flood waves in the presence of an isolated building or building array in an inundated area. Firstly, the proposed 2D numerical model was based on the finite-volume method (FVM) to solve 2D shallow-water equations (2D-SWEs) on structured mesh. The flux-difference splitting method (FDS) was utilized to obtain an exact mass balance while the Roe scheme was invoked to approximate Riemann problems. Secondly, the 3D commercially available CFD software package was selected, which contained a Flow 3D model with two turbulent models: Reynolds-averaged Navier-Stokes (RANs) with a renormalized group (RNG) and a large-eddy simulation (LES). The numerical results of an impact force on an obstruction due to a dam-break flow showed that a 3D solution was much better than a 2D one. By comparing the 3D numerical force results of an impact force acting on building arrays with the existence experimental data, the influence of velocity-induced force on a dynamic force was quantified by a function of the Froude number and the water depth of the incident wave. Furthermore, we investigated the effect of the initial water stage and dam-break width on the 3D-computed results of the peak value of force intensity.

scholarly journals Large Temperature Fluctuations due to Cold-Air Pool Displacement along the Lee Slope of a Desert Mountain

2017 ◽  
Vol 56 (4) ◽  
pp. 1083-1098 ◽  
Author(s):  
Matthew E. Jeglum ◽  
Sebastian W. Hoch ◽  
Derek D. Jensen ◽  
Reneta Dimitrova ◽  
Zachariah Silver
Keyword(s):  
Low Frequency ◽  
Temperature Fluctuations ◽  
Atmospheric Modeling ◽  
Large Temperature ◽  
Complex Flow ◽  
Near Surface ◽  
Cold Air ◽  
Flow Interactions ◽  
Initial Drop ◽  
Program Temperature

AbstractLarge temperature fluctuations (LTFs), defined as a drop of the near-surface temperature of at least 3°C in less than 30 min followed by a recovery of at least half of the initial drop, were frequently observed during the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) program. Temperature time series at over 100 surface stations were examined in an automated fashion to identify and characterize LTFs. LTFs occur almost exclusively at night and at locations elevated 50–100 m above the basin floors, such as the east slope of the isolated Granite Mountain (GM). Temperature drops associated with LTFs were as large as 13°C and were typically greatest at heights of 4–10 m AGL. Observations and numerical simulations suggest that LTFs are the result of complex flow interactions of stably stratified flow with a mountain barrier and a leeside cold-air pool (CAP). An orographic wake forms over GM when stably stratified southwesterly nocturnal flow impinges on GM and is blocked at low levels. Warm crest-level air descends in the lee of the barrier, and the generation of baroclinic vorticity leads to periodic development of a vertically oriented vortex. Changes in the strength or location of the wake and vortex cause a displacement of the horizontal temperature gradient along the slope associated with the CAP edge, resulting in LTFs. This mechanism explains the low frequency of LTFs on the west slope of GM as well as the preference for LTFs to occur at higher elevations later at night, as the CAP depth increases.

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