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Professor Robert Dorrell's Qualifications (2)

Doctor of Philosophy
PhD / DPhil

Status Complete
Part Time No
Years 2006 - 2010
Project Title Particulate Suspensions: The Mechanics of Suspension and Deposition
Project Description Modelling suspensions of particulate material allows us to understand a range of industrial and environmental problems. In particular we note that the behaviour of geophysical flows, such as turbidity currents, is dependent on the suspension and sedimentation of particulate material.

We initially model the sedimentation behaviour of suspensions in an otherwise quiescent fluid. The sedimentation of the particulate suspension is modelled as a continuum, by describing mass conservation in the flow. Analytical solutions are derived for the sedimentation of mono- and bidisperse suspensions. These solutions are used to validate numerical methods for solving sedimentation problems. The numerical methods, extended to model polydisperse suspensions, are quantitatively compared to experimental studies of quiescent settling problems.

A mass conservation model is used to describe the resuspension of particulate material by turbulent fluid motion. The depositional behaviour of dilute particulate suspensions, from waning turbulent fluid flows, is studied. This depositional behaviour is characterised by the time scale of response of the suspension to changes in flow conditions. Using this theoretical model, and with reference to recent experimental work, we explain various traits of the deposit structure generated by geophysical flows.

Further we study highly concentrated particulate suspensions in turbulent fluid flows, using a momentum conservation model. Using this model we validate the use of the previously discussed dilute model, in various flow scenarios. We also use the model to compare the predicted behaviour of recent experiments modelling geophysical flows to the predicted behaviour of such flows.

We conclude that simple mathematical models describing the sedimentation from particulate suspensions may quantitatively and qualitatively reproduce some of the depositional features of some geophysical flows. These models allow us to explain some of the key physics of particle sedimentation, in a range of different problems.
Awarding Institution University of Bristol