Author(s): M. Tregnaghi; A. Bottacin-Busolin; S. J. Tait; A. Marion

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Abstract: Experimental tests were carried out in a tilting laboratory flume using a modified 3D Particle Image Velocimetry (PIV) system. A gravel bed deposit was placed in the flume and subjected to steady, uniform flows that caused a range of sediment transport mobilities. Flow velocity measurements were made, at a frequency of 45Hz and at a grain scale spatial resolution, over an area of 220x40 mm 2, on a plane located just above the original sediment bed. Image processing and cross-correlation techniques were used to obtain the flow velocity time series in this measurement plane. An additional camera provided sequences of images of the bed surface, at the same location, which were taken simultaneously with the measurements of the flow field. By comparing grain motion in the bed camera images with the velocity data, changes in the local flow field can be linked with the entrainment or deposition of individual particles, , either in terms of any of the three velocity components or in terms of the relevant Reynolds stresses. The experimental data set contained the movement of hundreds of grains from tests exhibiting a range of average sediment mobilities. Using this knowledge work is continuing to develop statistically based models of grain entrainment for natural sediment at a range of flow conditions.

DOI:

Year: 2010