Schools of Geosciences and Engineering
College of Physical Sciences

PhD Studentship

Project title: Turbulence Structure and Sediment Transport in River Plumes

Project Description: The fresh water discharging from rivers into the ocean is buoyant with respect to the denser salty sea-water, and so forms a plume that spreads over the ocean surface. The plume carries a considerable proportion of the suspended sediment in the river and, subsequently to settle out on the sea-floor at some distance from the river mouth. This is the source of over 90% of the sediment that reaches the ocean - the ultimate sink for all of the material eroded from the continents. It is thus of immense importance in the global sediment budget, in the composition and architecture of sediment accumulations on continental margins, and in the hydrocarbon source potential of marine sediments.

Turbulent suspension is one of the main processes in which sediment is carried ocean-wards within plumes. But to date our understanding of the physical basis of this process is, at best, sketchy. The fine-scale turbulence structure of plumes has not been investigated in detail, nor the relative importance of turbulence-generating mechanisms (buoyancy, internal shear and interfacial processes at the lower and upper boundary), still less the effect of these on the maintenance of sediment suspension.

The project will involve the generation of buoyant plumes at Fluid Mechanics laboratory and will be carried out in two stages. The first stage will focus to investigate the turbulence structure of non-opaque (i.e. sediment-free) using state-of-the-art optical techniques for the elucidation of turbulence structure (namely particle-image-velocimetry (PIV), laser Doppler velocimetry (LDV) and laser holography) in addition to various visualisation techniques, and also acoustic velocimetry techniques, which are already available in Fluid Mechanics Laboratory of the Engineering School. The research work in the second stage of the project will concentrate on the investigation of the distribution of suspended sediment with respect to the dynamic properties of plumes as well as the ambient turbulence structure. The experimental work will be accompanied by the execution of numerical simulations using available computational fluid dynamics software (Fluent), for which UoA has licences. In addition to complementing the experiments, these simulations will be used to aid in the design of a facility for future work on plumes.

The project will run in parallel with large-scale sedimentation experiments and with high-resolution numerical simulations being carried out respectively at Universidade do Rio Grande do Sul, Brazil, and University of California at Santa Barbara, USA, (at both of which BK has visiting positions), and concurrently with several studentships in Aberdeen investigating the geology of large river-fed sediment accumulations.

The project is funded by the Knowledge Transfer Grant of Aberdeen University and BG group.

More information: Informal enquiries can be made to the supervisors, Professor Ben Kneller b.kneller@abdn.ac.uk, Professor Vladimir Nikora v.nikora@abdn.ac.uk or Dr Yakun Guo y.guo@abdn.ac.uk.

Online application forms and application guidelines can be found at http://www.abdn.ac.uk/sras/postgraduate/apply.shtml

Applications should be submitted to the College of Physical Sciences Graduate School http://www.abdn.ac.uk/cops/graduateschool/

Application Deadline: 1 June 2008

Start Date Deadline: 31 July 2008