The local dynamics of sandwaves and their crest-shedding turbulent flows has received little mechanistic attention, unlike recent advances in allied fields such as bubbly shear flows. One main purpose of the present project is to address these questions of particle engagement and transport by transient large eddies in the free shear layer over sandwaves. Experimental studies were conducted on the trajectories of model particles over suitably scaled fixed bedforms in a purpose built flume. Three important results emerged. Firstly, trajectories of particles jetted over the crest fell into seven primary modes from short paths beyond the crest to extended downstream transport. Secondly, the vertical profiles of particle concentration exhibited peaks at crest elevation over the trough, comparing with recent field observations by (Soulsby, 1989). Thirdly, flapping excursions of the shear layer were found to enhance lee slope scour and probably account for the sediment clouds observed in Soulsby's field study, here further conjectured to result in sandwave washout at high flow velocities. Favourable comparisons with previous studies are described.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:583082 |
| Date | January 1995 |
| Creators | Onslow, Roland James |
| Publisher | University of Birmingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://etheses.bham.ac.uk//id/eprint/4533/ |
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