Details of Grant 

EPSRC Reference:	EP/H007032/1
Title:	Sediment transport and resuspension by grid turbulence
Principal Investigator:	Munro, Dr R
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Department:	Div of Process and Environmental Eng
Organisation:	University of Nottingham
Scheme:	First Grant - Revised 2009
Starts:	01 December 2009	Ends:	30 November 2011	Value (£):	102,285
EPSRC Research Topic Classifications:	Fluid Dynamics Multiphase Flow
EPSRC Industrial Sector Classifications:	Chemicals Water
Related Grants:
Panel History:	Panel Date Panel Name Outcome 16 Jun 2009 Process Environment and Sustainability Announced
Summary on Grant Application Form
The erosion, transport and deposition of sediment is an important phenomenon in many industrial, environmental and geophysical processes. Common examples include sewage filtration systems, sand drift and dust storms in deserts, and the transfer of sediments from land to oceans by the combined effects of coastal, river and wind erosion. For instance, the global flux of sediment into the oceans from the continents is estimated to be over 18 billion tons per year. Notably, less than 4% of this is caused by wind and coastal erosion, but over 64% is deposited due to suspended sediment loads carried by the World's rivers (with the largest depositers being rivers like the Amazon and Ganges).Predicting how a fluid (necessarily turbulent) transports or resuspends sediment requires specifying a relation giving the sediment flux in terms of the flow characteristics. Existing models characterise the flow in terms of spatially or temporally averaged quantities, such as the mean streamwise velocity or bed shear stress. In this way, the sediment flux is linked to parameters that are relatively easy to measure or predict. However, sediment entrainment and transport are neither driven by bed shear stress nor any other average flow characteristic, but instead by the fluctuating forces, such as lift and drag, exerted on individual sediment grains by the flow. Average flow parameters can only provide, at best, a parameterisation of the underlying physical controlling these processes. It is now widely recognised that clarification of the complex physics associated with the sediment-turbulence iteration is essential, not only to improve current understanding, but also to significantly improve accuracy of current sediment transport models and formula.This proposal describes experiments designed to investigate, in detail, how the range of motion scales within a fully turbulent flow act to move and resuspend sediment grains. Specifically, the experiments will study the sediment-turbulence interaction in the simplified context of zero-mean turbulence generated by an oscillating grid. Here, the turbulence is isolated from the effects of a mean flow, allowing for a simplified but detailed analysis of how the fluctuating turbulence components interact with, displace and resuspend the sediment. The controllable and repeatable nature of (statistically) steady grid turbulence also provides an ideal mechanism for accurately inducing the flow conditions required to initiate sediment transport and resuspension.Advanced time- and spatially-resolved measurement systems [Laser Doppler Velocimetry (LDV), Particle Imaging Velocimetry (PIV), high-speed cameras] will be used to obtain detailed measurements of the fluctuating turbulence velocity components in the region close to the sediment layer. By using a mixture of black and white sediment grains, the pattern-matching technology associated with PIV will also be further developed (by considering the black sediment particles as tracers) to measure the velocity and trajectory of sediment grains displaced by the action of the fluid flow. The data obtained will be analysed using a combination of spectral and time-correlation techniques to identify the dominant scales within the turbulence spectrum which cause sediment transport and resuspension, and to identify the important role coherent vortex structures (or energy-containing eddies) play in these processes.So that the effects of sediment type and bed roughness can be analysed, a range of different particle sizes and densities will be considered (mono- and poly-disperse) with diameters ranging between 150-4000micron and relative densities between 1.2 and 3.5. Notably, the apparatus is designed to allow the important effects of bed slope to also be analysed, in particular, as the bed slope approaches the repose limit. The experiments will focus on the critical flow conditions needed to initiate sediment movement and resuspension.
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Organisation Website:	http://www.nottingham.ac.uk