WP 3: Benchmarking - Flood Propagation

S. SOARES FRAZÃO Dept. Civ. and Env. Engrg., Université catholique de Louvain, Belgium
soares@gce.ucl.ac.be

Y. ZECH Dept. Civ. and Env. Engrg., Université catholique de Louvain, Belgium
zech@gce.ucl.ac.be

1. Introduction
2. Test case Desciption
    2.1 Location of the gauges
    2.2 Location of the building
    2.3 Initial Conditions
    2.4 Boundary Conditions
    2.5 Expected results
3. Acknowledgements

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Submission Guidelines

This test case aims at investigating the effects of a single building on a dam-break flow. It is part of the broader study of flood propagation in urban areas undertaken within the frame of the IMPACT project.

In preliminary studies, it appeared that, especially in the first instants after the dam break and the immediate vicinity of the dam, buildings can have major consequences on the flow. In those cases, they cannot be considered only as inducing a reduced flow conveyance or an increased bed friction slowing down the wave propagation. Indeed, the flow route can be modified, or the flood wave can reflect against the building, increasing the upstream water depths dramatically.

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In order to investigate those near-field effects, and with the aim to assess the consequences further downstream in the valley and at later times, this idealised test case has been designed. The experiments were carried out in the Civil Engineering Laboratory of the Université catholique de Louvain (UCL) in Belgium. The channel and building dimensions are indicated on the sketch (see last page), as well as the position of the water level gauges used to record the time evolution of the water level. Note that the channel (and reservoir) cross section has a trapezoidal shape near the bed. The gate is located between two impermeable blocks and the cross section there is rectangular and narrower than the channel cross-section. The channel bed is horizontal.

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The location of the gauges is indicated on the sketch. Their exact position regarding the origin of the axis (centre of the gate) is summarised in the following table :

		x (m)	x (m)
G1		2.65	1.15
G2		2.65	-0.60
G3		4.00	1.15
G4		4.00	-0.80
G5		5.20	0.30
G6		-1.87	1.10

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The location and dimensions of the building are indicated on the sketch. The exact co-ordinates of the four corners of the building regarding the origin of the axis (see sketch) are summarised in the following table:

		x (m)	x (m)
b1		3.40	-0.05
b2		3.76	-0.23
b3		4.11	0.49
b4		3.75	0.67

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Water depth in the reservoir : h₀ = 0.40 m
Water depth in the channel : h₀ = 0.01 m

To simulate the dam break, the gate separating the reservoir from the channel is pulled up rapidly, resulting in an instantaneous dam break.

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The upstream end of the channel is a closed wall. At the far downstream end of the channel (ca. 29 m from the gate), there is sediment settling system making this boundary an unclear combination of weirs and walls. However, it was observed that there is no influence of this boundary condition during the first 30 seconds after the dam break. It is thus left to the modeller to use any downstream boundary condition he likes provided this does not influence the flow during the duration of the experiment.

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• Short description of the numerical simulation including
• The numerical method used, or a reference where a description of the method can be found;
• The type of mesh used (square, rectangular, triangular, quadragular), the number of computational cells or points, the duration of the simulation (real time elapsed during the computation);
• Comments regarding the results and the simulation, if any.
• Results at the gauging points (G1 … G6): a text file with the following format (thus 1 file)
  
  

Col 1	Col 2	Col 3	Col 4	...	Col 17	Col 18	Col 19
Time(s)	G1 water depth (m)	G1 u-velocity (m/s)	G1 v-velocity (m/s)	...	G6 water level (m)	G6 u-velocity (m/s)	G6 v-velocity (m/s)
...	...	...	...	...	...	...	...

The experimental measurements were recorded with a time step of 0.01 s.

• Water level and velocities over the whole channel at the following specific times : t = 1 s, 5 s, 10 s, 20 s, with the following file format for each time (thus 4 files)

Col 1	Col 2	Col 3	Col 4	Col 5
x (m)	y (m)	h water (m)	u (m/s)	v (m/s)
...	...	...	...	...

Please note that the origin of the axis is located at the centre of the gate (see sketch). The u and v velocities are the velocity components according to the x and y directions.

Click on the image to see a larger version

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The authors wish to acknowledge the financial support offered by the European commission for the IMPACT project under the fifth framework programme (1998-2002), environment and sustainable development thematic programme, for which Karen Fabbri was the EC project officer.

To view the PDF document for the isolated building test case click here.
(Note: To download the PDF document right-click on the link and select 'Save Target As'.)

• The deadline for submisison of results is 31 May 2003
• Please email results and questions to either Benjamin Noel or Sandra Soares

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