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Free Surface Flow Through Homogeneous Bottom Roughness

Author(s): H. Romdhane; A. Soualmia; L. Cassan; D. Dartus

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Abstract: The flow in channels and rivers is strongly influenced by the roughness of the channel bottom, by the presence of vegetation or other obstacles. In this context, an experimental study was conducted in the laboratory of the Institute of Fluid Mechanics of Toulouse “IMFT” . The experimental design is a rectangular channel 4 m long and 0.4 m wide and 0.8 m deep. The bottom has a homogeneous roughness contrast (installation of a mat). For the measurement of speed, the channel is equipped with a fast camera. The originality of our work lies in the application of a PTV particle tracking technique (Particle Tracking Velocimetry). It is a non-intrusive measurement technique to measure instantaneous speed two-dimensional fields in stationary and unsteady flows. It involves seeding the flow through reflective particles, with the same density as the fluid, which will be lit using a lighting plan. Analysis of the results is by processing images taken by the camera using Quick Matlab that is suitable for our case study. The obtained results show a depression of the maximum speed below the free surface. This behavior indicates a delay of the flow in the vicinity of the free surface and this is a direct consequence of the presence of secondary flows in these areas. These conducted measurements allowed the determination of wall parameters which are fundamental.

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Year: 2016

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