Alan Cuthbertson, Farzin Samsami, Olugbenga Samuel Ibikunle

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Results are presented from a series of parametric experiments investigating the time-dependent flocculation characteristics for sand-mud suspensions under stationary, nearly-isotropic, grid-generated turbulence. The experimental runs were conducted in a sophisticated 2.1 m by 0.25 m diameter settling column, incorporating a fixed array of oscillating grids to generate predictable and repeatable zero-mean-shear turbulent flow fields under a range of hydrodynamic forcing conditions. Experimental measurements focused on determining the temporal development of mud flocs for different sand-mud mixtures through in-situ visualization and measurement of their geometric properties under specific grid shear conditions generated within the column. In-situ total suspended sediment (TSS) concentration measurements were also obtained at the mid-height and bottom of the main column using calibrated optical backscatter sensor (OBS) probes. The results indicated that, for mud-only suspensions, the measured peak and significant floc sizes increased non-linearly with measured TSS values, while higher values of grid-generated shear rate tended to reduce floc sizes attained within the column. On addition of the sand fraction, smaller overall floc sizes were also attained compared to the mud-only runs, suggesting that the sand particles impose an additional break-up mechanism on the developing flocs, either through direct collisions between sand particles and mud flocs and/or induced shear caused by differential settling effects. In this regard, it is anticipated that the study findings will provide enhanced understanding of sand-mud interactions within mixed suspensions leading to improved representation in mixed sediment transport models (e.g. through the development of population balance models with interactions between multiple sediment fractions).
Original languageEnglish
Title of host publicationE-proceedings of the 36th IAHR World Congress 28 June – 3 July, 2015, The Hague, the Netherlands
Number of pages4
Publication statusPublished - 2015


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