Investigation of dam-break flood waves in a dry channel with a hump

• The current paper highlights the effects of an abrupt change in bottom topography and of the presence of upward and downward bed slope on propagation of dam break flood waves.
• A new experiment was carried out concerning a dam break flow in an initially dry flume with a hump. An advanced measuring technique, based on digital image processing, was used to acquire water depths. The free surface profiles and stage hydrographs were satisfactorily obtained in a simple and economical way with non-intrusive measurements.
• The numerical simulation of the problem was performed by VOF-based CFD involving two different approaches: SWE and RANS. Comparison between the computed results and the experimental data shows good agreements.

Dam-break represents a potential flood hazard for population at downstream due to the sudden release of the water stored in the reservoir. The prediction of dam-break wave parameters is complicated furthermore by the presence of irregularities in the channel. This paper aims to present an experiment and numerical simulations of dam-break flood wave in an initially dry flume with a hump. A triangular-shaped bottom obstacle was placed downstream the dam site in the channel to provide the effects of both bottom slope and abrupt change in topography on propagation of dam-break flood waves. A new experiment was carried out in a smooth rectangular cross-section channel by using digital image processing. Flow behaviour was synchronously recorded with three adjacent CCD cameras through the glass walls of the entire downstream channel. This adopted measuring technique eliminates the necessity for test repetition due to capturing the whole flow field at once. Not only continuous free surface profiles at various times but also time evolutions of the water levels for selected locations were simply acquired from the video records of the image processing by virtual wave probe. Furthermore, dam-break flow was numerically simulated by the VOF-based CFD commercial software package FLOW-3D, which utilizes two distinct approaches, namely the Reynolds-averaged Navier–Stokes equations (RANS) with a k-ε turbulence model and the simple Shallow Water Equations (SWEs). Comparison between the computed results and the experimental data shows that both numerical models reproduce the flow behaviour with reasonable accuracy and the agreement is slightly better in RANS model compared to simple SWE model. Current experimental data can be useful for validation of other numerical models.