The settling velocity of sediments in laboratory by using Particle Tracking Velocimetry (PTV)
Pelissou, L. (2024). The settling velocity of sediments in laboratory by using Particle Tracking Velocimetry (PTV). Thesis. Polytech/Flanders Hydraulics: [s.l.]. 24 pp.
In all water courses, sediment transport regulates and influences the flows. Thus, engineers try to model this behaviour to predict the movements and be able to react in consequences as during dredging for example. It is therefore necessary for them to know and enter target values of the area studied in their models to have results closest to reality; these include the settling velocity.The sedimentation velocity has been extensively studied and many formulas are available to calculate it. In this report, it is studied experimentally and then compared to theoretical values.First, the different instruments and software used are described: a camera, a white light spot, a laser, a water tank and a computer with various software. To make the recordings, two software are needed, one to make the adjustments and the other to make sequences of images. To analyze these images, another software is needed: Streams. Its operation relies on objects and pipelines. It allows to identify the particles on the photos, to match them and to deduce the fall velocity.The different tools used require settings and, in this report, I focused on finding the various optimal parameters to obtain the best results, like the frame rate, light intensity and particle identification method. The laser allows the identification of a larger number of particles but does not improve the tracking of particles in images and therefore in terms of complexity of implementation, it was concluded that white light seems more appropriate.In order to use this method to define the settling velocity in the Scheldt, the repeatability of the operation and consistency with the theory were tested. For this, a sample of sediment mixed with water was prepared and the same experiment was carried out ten times. These tests showed that the calculated fall velocity was not stable and did not correspond to the theory. Different explanations were then submitted (the analysis on Streams or the sediments used) but none explains these differences.
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