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Scouring at the Interface Between Fixed and Mobile Bed in Steep Sloped Channels

Author(s): Fabian Franzini, Tzu Yin Chen, Hervé Capart, Sandra Soares-Frazao

Linked Author(s): Sandra Soares-Frazao

Keywords: Erosion processes, flow-structure interactions, flow visualization and imaging, laboratory experiments, Particle Tracking Velocimetry (PTV)

Abstract: The intense scouring occurring at the interface between fixed and mobile bed can have a strong impact on the stability of structures and on the global morphological changes in rivers. Often, this transition is studied in flat or mild-slope channels. However, in order to better understand this phenomenon, it is important also to understand what can happen in steeper channels. The research presented here focuses on an experimental study of scouring at the interface between fixed-mobile beds in a steep channel with a 5% bed slope. The experiments are conducted in an 8 m long flume featuring a 2 m long fixed bed followed by a mobile bed portion. Results are captured using two types of cameras: a classical camera capturing 12 pictures per second and a high-speed camera capturing 500 pictures per second. The first one is used to capture the bed- and water-level evolution during the scouring process. The second one allowed the study of the movement of the individual sand particles. The flow is controlled by a fixed discharge upstream and a 0. 30 m high weir downstream. The experiments are run using four different constant discharges. All tests are repeated 3 to 5 times and showed good repeatability. The results highlighted four different stages in the scouring process as well as the links between the velocity field and the evolution of the bed morphology. The experimental results are then compared to numerical simulations using a one-dimensional finite-volume model


Year: 2017

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