Study of dam break flow interaction with urban settlements over a sloping channel

This paper describes a dam break experiment on a sloped channel, carried out in a hydraulic flume at UCL for the purpose of computer model validations of extreme events, such as flash floods. An elevated reservoir was situated upstream followed by a 1/20 slope leading up to a flat floodplain. Plexiglas blocks were positioned on the floodplain constituting different urban settlements and creating different obstructions to the flow. The flume was instrumented along its length measuring the change in water depth in the reservoir; the water depth time histories in various locations; the flow patterns and flood front velocity; and lastly the pressure and load on the buildings. The experiments were repeated for different urban settlements, flood intensities (two different initial water depths in the reservoir) and roughness layers along the slope, representative of a vegetated and a non-vegetated hill. In the present study, the experimental results were described qualitatively and compared with theoretical processes and 2D numerical results obtained using OpenFOAM's RAS turbulent model. Water depth, velocity and load measurements were analysed for different cases and it was found that while the 2D model provided a good fit on the slope, the flows generated around the building were more complex 3D formations which lead to inaccuracies. All experiments were repeated multiple times to ensure repeatability and thus the procedure was validated successfully providing a complete dataset that can be used for the validation of computational models for extreme events.

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

Water ◽

10.3390/w13030344 ◽

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.

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2D numerical modelling of dam break- applying for Namchien dam in Vietnam

International Journal of Innovative Technology and Exploring Engineering - Special Issue ◽

10.35940/ijitee.i7825.078919 ◽

2019 ◽

Vol 8 (9) ◽

pp. 711-716

Keyword(s):

Dam Break ◽

Arch Dam ◽

Roughness Coefficient ◽

Proposed Model ◽

Nonlinear Shallow Water Equations ◽

Time Histories ◽

Friction Term ◽

Dam Break Flow ◽

High Roughness ◽

Volume Method

The paper is dedicated to study a numerical model simulating dam-break based on two dimensional nonlinear shallow water equations (2D-NSWE). Finite Volume Method-Godunov type is applied to discretize this equation. Roe scheme is utilized to approximate Riemann problem, meanwhile method of flux difference splitting is implemented to construct numerical solvers of SWE. Besides, the semi implicit scheme is also invoked to solve friction term in case of high roughness coefficient. The proposed model is verified through a comparison between computed results and empirical data of two reference tests. A dam break flow over floodable area with different roughness coefficients is also researched. A total collapsed dam scenario of an arch dam-Nam Chien in Vietnam is simulated by the proposed model. Several hydraulic characteristics such as flood extent, arrival time and time histories of water depth at different gauges are estimated with different grid sizes.

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An Experimental Study of the Run-Up Process of Breaking Bores Generated by Dam-Break Under Dry- and Wet-Bed Conditions

Journal of Earthquake and Tsunami ◽

10.1142/s1793431118400055 ◽

2018 ◽

Vol 12 (02) ◽

pp. 1840005 ◽

Cited By ~ 4

Author(s):

Senxun Lu ◽

Haijiang Liu ◽

Xiaohu Deng

Keyword(s):

Water Depth ◽

Laboratory Experiments ◽

Bottom Friction ◽

Dam Break ◽

Hydrodynamic Characteristics ◽

Initial Water ◽

Water Head ◽

Run Up ◽

Front Profile ◽

Two Stages

In this study, a series of dam-break laboratory experiments were carried out to investigate the run-up process of breaking bores under dry- and wet-bed conditions. Detailed measurements were conducted to reveal differences in the run-up hydrodynamic characteristics under these two conditions, e.g. the bore front profile, the maximum run-up height and duration, and the instantaneous bore front velocity. Two successive bores were observed under the wet-bed run-up process, while multiple bores (three bores in general) were generated during the dry-bed run-up process due to the significant bottom friction effect. A linear relationship with the uniform gradient is found between the maximum run-up height and the initial water head for both dry- and wet-bed conditions, indicating that difference in the maximum run-up height between the dry- and specified wet-bed cases or among various wet-bed cases is not sensitive to the initial water head. Under the same initial water head, although the dry-bed run-up process takes a longer duration than that of wet-bed cases, the maximum run-up height is smallest for the dry-bed case and gradually increases with the increase of the initial downstream water depth for wet-bed cases. Under the wet-bed conditions, temporal variation of the bore front run-up velocity can be classified into two stages, i.e. the acceleration stage induced by the relatively large incident bore front water depth (large onshore hydrostatic pressure gradient) and the deceleration stage governed by the offshore-directed gravity force and bottom friction. Nevertheless, due to the small incident bore front water depth, run-up process under the dry-bed conditions does not show the acceleration stage.

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On a dam-break flow in a channel of constant water depth.

Doboku Gakkai Ronbunshu ◽

10.2208/jscej.1985.363_79 ◽

1985 ◽

pp. 79-86 ◽

Cited By ~ 1

Author(s):

Hideo MATSUTOMI

Keyword(s):

Water Depth ◽

Dam Break ◽

Dam Break Flow

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EXPERIMENTAL AND THEORETICAL STUDY ON FLOOD BORE PROPAGATION AND MUSHROOM JET GENERATION OF DAM-BREAK FLOW

Visualization of Mechanical Processes An International Online Journal ◽

10.1615/vismechproc.v1.i3.30 ◽

2011 ◽

Vol 1 (3) ◽

Author(s):

H. H. Hwung ◽

Ray Yang ◽

Y. C. Tie ◽

W.Y. Hsu ◽

P. C. Kuo ◽

...

Keyword(s):

Theoretical Study ◽

Dam Break ◽

Dam Break Flow

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

Journal of Marine Science and Engineering ◽

10.3390/jmse9010067 ◽

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.

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