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Title: The effects of upstream sediment supply on the movement of mixed grain sediment
Author: Wheeler, Max Vernon Charles
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1994
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The sediment transport process for non-uniform mixtures involves a complex dynamic interaction between the material transported, the surface texture and the flow regime. However, the respective influence of each of these on the other, and on the transport rate is not well understood. The primary objective of this experimental study, was to consolidate and extend the understanding of these processes by investigating sediment transport, near bed flow structures and surface texture simultaneously, as various sediment mixtures were input upstream at differing feed rates, onto mobile mixed grain sediment beds. Three sets of laboratory experiments were completed. The first set of experiments were not fed with material, and acted as reference for later experiments. The second set, fed on two separate occasions, onto an already mobile gravel bed, two different sized uniform materials. Material was fed at a fixed rate that was similar in both runs. The third set of runs, fed material mixtures (again onto an already mobile gravel bed) at a rate that was fixed during each experiment, periodic measurements were made of bedload transport rates, bedload composition, bed surface texture and the near bed flow regime. Results showed that the stability of mixed grain bed was strongly influenced by the feed rate and composition of the upstream sediment supply. A relationship between the surface texture and the moving grain triggered a grain interaction process, which was thought to be as important as the fluid forces in governing the sediment transport rate. The interaction process either enhanced bed stability or promoted sediment movement. How the system responded was determined by the flow regime, the extent of surface texturing and the grain size distribution of the moving grains.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available