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Computational dam-break hydraulics over erodible sediment bed

Computational dam-break hydraulics over erodible sediment bed
Computational dam-break hydraulics over erodible sediment bed
This paper presents one of the first dedicated studies on mobile bed hydraulics of dam-break flow and the induced sediment transport and morphological evolution. A theoretical model is built upon the conservative laws of shallow water hydrodynamics, and a high-resolution numerical solution of the hyperbolic system is achieved using the total-variation-diminishing version of the second-order weighted average flux method in conjunction with the HLLC approximate Riemann solver and SUPERBEE limiter. It is found that a heavily concentrated and eroding wavefront first develops and then depresses gradually as it propagates downstream. In the early stage of the dam-break, a hydraulic jump is formed around the dam site due to rapid bed erosion, which attenuates progressively as it propagates upstream and eventually disappears. While the backward wave appears to migrate at the same speed as over a fixed bed, the propagation of the forward wavefront shows a complex picture compared to its fixed-bed counterpart as a result of the domination of rapid bed erosion initially, the density difference between the wavefront and the downstream ambient water in the intermediate period, and the pattern of the deformed bed profile in the long term. It is also found that the free surface profiles and hydrographs are greatly modified by bed mobility, which has considerable implications for flood prediction. The computed wave structure in the intermediate period exhibits great resemblance to available experiments qualitatively, and yet the existence of a shear wave is found in lieu of a secondary rarefaction postulated in an existing analysis. Finally, the use of the complete, rather than simplified, conservation equations is shown to be essential for correct resolution of the wave and bed structures, which suggests that previous models need reformulating.
689-703
Cao, Z.
c541462a-b279-4c97-910d-69a6726c57c6
Pender, G.
bfa21491-dce6-485e-ae46-bd63b08efb75
Wallis, S.
4cf0446d-66d9-471c-a524-3faa09a5fd06
Carling, P.A.
8d252dd9-3c88-4803-81cc-c2ec4c6fa687
Cao, Z.
c541462a-b279-4c97-910d-69a6726c57c6
Pender, G.
bfa21491-dce6-485e-ae46-bd63b08efb75
Wallis, S.
4cf0446d-66d9-471c-a524-3faa09a5fd06
Carling, P.A.
8d252dd9-3c88-4803-81cc-c2ec4c6fa687

Cao, Z., Pender, G., Wallis, S. and Carling, P.A. (2004) Computational dam-break hydraulics over erodible sediment bed. Journal of Hydraulic Engineering, 130 (7), 689-703. (doi:10.1061/(ASCE)0733-9429(2004)130:7(689)).

Record type: Article

Abstract

This paper presents one of the first dedicated studies on mobile bed hydraulics of dam-break flow and the induced sediment transport and morphological evolution. A theoretical model is built upon the conservative laws of shallow water hydrodynamics, and a high-resolution numerical solution of the hyperbolic system is achieved using the total-variation-diminishing version of the second-order weighted average flux method in conjunction with the HLLC approximate Riemann solver and SUPERBEE limiter. It is found that a heavily concentrated and eroding wavefront first develops and then depresses gradually as it propagates downstream. In the early stage of the dam-break, a hydraulic jump is formed around the dam site due to rapid bed erosion, which attenuates progressively as it propagates upstream and eventually disappears. While the backward wave appears to migrate at the same speed as over a fixed bed, the propagation of the forward wavefront shows a complex picture compared to its fixed-bed counterpart as a result of the domination of rapid bed erosion initially, the density difference between the wavefront and the downstream ambient water in the intermediate period, and the pattern of the deformed bed profile in the long term. It is also found that the free surface profiles and hydrographs are greatly modified by bed mobility, which has considerable implications for flood prediction. The computed wave structure in the intermediate period exhibits great resemblance to available experiments qualitatively, and yet the existence of a shear wave is found in lieu of a secondary rarefaction postulated in an existing analysis. Finally, the use of the complete, rather than simplified, conservation equations is shown to be essential for correct resolution of the wave and bed structures, which suggests that previous models need reformulating.

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Published date: 2004

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Local EPrints ID: 15517
URI: http://eprints.soton.ac.uk/id/eprint/15517
PURE UUID: 1b2543d5-7c6f-44e1-8cbc-2fba980bba2a

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Date deposited: 20 Apr 2005
Last modified: 15 Jul 2019 19:32

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