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Effect of Hydrodynamics Factors on Flocculation Processes in Estuaries

Author(s): A. Mhashhash; B. Bockelmann-Evans; S. Pan

Linked Author(s): Shiyang Pan

Keywords: No keywords

Abstract: Cohesive sediment flocculates under certain conditions to form flocs which are larger than individual particles and less dense. The flocculation has an important role in sediment transport processes of settling, deposition and erosion. In this study, well controlled laboratory experiments were performed to investigate the effect of turbulence on floc size and settling velocity. Experimental research was conducted in a 1 L glass beaker of 11 cm diameter using suspended sediment samples taken from the Severn Estuary. A PIV system and image processing routine were used to measure the floc size distribution and settling velocity, as well as the flocs density. This study found that turbulent shear stress in a range from 0.57 to 8.5 N/m 2 would cause a breakdown in floc structure. The settling velocity of the samples was found to range from 0.4 to 1.4 mm/s. The average settling velocity increased with the increase of the turbulent shear stress up to the maximum value (1.1 mm/s), and then decreased. It was also found that the relationship between floc size and turbulence were independent of the history of the floc formation.

DOI:

Year: 2016

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