Dam break experiment over a mobile bed : determination of the bed shear stress based on velocity profile measurements
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- Dams have been part of our world for decades and lately, their number notably increased especially in the hydro-power field. A larger number of structure involves a larger risk of failure. Dam-break events rarely occur but are still happening to this day. The consequences of this catastrophes are not well defined yet, in particular the water and the bed sediment behaviour. The erosion of the soil and the topographical impact resulting from a dam failure have not been precisely defined. This master thesis aims to explore these imprecise phenomenons by characterizing in a better way the shear stress in the water-sediment boundary, based on the water velocity profiles. To achieve this, we had at our disposal an hydraulic laboratory. It contained a channel able to simulate a dam-break event. This simulation was the base of our analysis and helped us to understand the interactions between the water and the sediments. We proceeded to record the water velocity profiles necessary to determine the bed shear stress. Thus, we used a high-speed camera to capture the simulations by the mean of a non-intrusive tracer. The images gathered were then investigated throughout the software DaVis8 in order to obtain the horizontal velocity vectors of the water. From this point, two distinct theoretical methods were investigated to determine their effectiveness in a dam failure case. The Clauser method and the slope method are primarily intended to calculate the bed shear stress in common flows thanks to the velocity profiles but they could still be useful in our investigation. The simulations were made for several different initial conditions. We varied the sediments properties and the water height upstream the dam. We then compared the results of both methods and how they reacted to the different cases. Finally, we defined the limits for those methods and proposed changes to their theoretical formulas to adapt them to a dam-break case.
Citations
Pigeolet, X., & Toussaint, H. (2021). Dam break experiment over a mobile bed : determination of the bed shear stress based on velocity profile measurements. https://dial-mem.test.bib.ucl.ac.be/handle/2078.2/23367