19 research outputs found
The physics of sand transport by wind
SIGLEAvailable from British Library Document Supply Centre- DSC:DX175780 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Analysis of small-scale gravel bed topography during armouring.
NoIn evaluating the resistance of sediment particles to entrainment by the action of the flow in a river, the grain geometry is usually characterized using representative sizes. This approach has been dictated, initially by lack of physical insight, but more recently by the lack of analytical tools able to describe the 3-D nature of surface grain organization on water-worked sediment beds. Laboratory experiments are presented where mixed grain size beds were mobilized under a range of hydraulic and sediment input conditions. Detailed bed topography was measured at various stages. Statistical tools have been adopted which describe the degree of surface organization on water-worked sediment bed surfaces. The degree of particle organization and the bed stability can be evaluated in relative terms using the properties of the probability density distribution of the bed surface elevations and in absolute terms using a properly defined 2-D structure function. The methods described can be applied directly to natural water-worked surfaces given the availability of appropriate bed surface elevation data sets
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Sediment transport over a flat bed in a uni-directional flow: simulations and validation.
NoA discrete particle model is described which simulates bedload transport over a flat bed of a unimodal mixed-sized distribution of particles. Simple physical rules are applied to large numbers of discrete sediment grains moving within a unidirectional flow. The modelling assumptions and main algorithms of the bedload transport model are presented and discussed. Sediment particles are represented by smooth spheres, which move under the drag forces of a simulated fluid flow. Bedload mass-transport rates calculated by the model exhibit a low sensitivity to chosen model parameters. Comparisons of the calculated mass-transport rates with well-established empirical relationships are good, strongly suggesting that the discrete particle model has captured the essential elements of the system physics. This performance provides strong justification for future interrogation of the model to investigate details of the small-scale constituent processes which have hitherto been outside the reach of previous experimental and modelling investigations