HR: 16:55h
AN: H54E-04    [Abstracts]
TI: Modeling the Role of Small Scale Physics in Sediment Transport From Grain Size to Grain Shape
AU: * Calantoni, J
EM: joec@nrlssc.navy.mil
AF: Naval Research Laboratory, Marine Geosciences Division, Code 7440.3, Stennis Space Center, MS 39529, United States
AU: Holland, K T
EM: tholland@nrlssc.navy.mil
AF: Naval Research Laboratory, Marine Geosciences Division, Code 7440.3, Stennis Space Center, MS 39529, United States
AB: In recent years work has focused on the detailed physics of sediment transport at or near the grain scale. Although computational resources often restrict the domain size, deterministic models for sediment motions can prove useful in improving our understanding of sediment dynamics. Using a discrete particle model (DPM), we have performed computer simulations that describe the collective and individual motions of sediment grains immersed in fluid in an effort to emulate the physics of the sea floor, at the fluid-sediment interface, in shallow water under forcing from waves and currents. Examples of our DPM (briefly described) are shown for research applications at a range scales from millimeters to meters involving fluid flow models from simple one- dimensional eddy viscosity up to three-dimensional direct numerical simulation. Based on hundreds of different simulations over the past decade, our findings have shown: how a parameterization of pressure gradients or equivalently fluid accelerations on particle motions under waves influences sand bar migration in the surf zone; how grain shape changes bulk bedload transport rates; how efforts to model sediment particle motions in the swash zone can yield insight toward models for shoreline erosion and accretion; how recently simulated bedload transport using bimodal size distributions has uncovered a new power law; how upcoming work focuses on simulating the role of grain size distributions in small-scale sand ripple dynamics. Good agreement is found between comparisons of model output for both bulk transport rates and time dependent concentration profiles with laboratory data. Likewise, parameterizations obtained from simulation results have demonstrated skill in hindcast applications to both field and laboratory measurements. Conclusions will discuss the future role of reductionism in sediment transport modeling.
DE: 1862 Sediment transport (4558)
DE: 4217 Coastal processes
DE: 4255 Numerical modeling (0545, 0560)
DE: 4546 Nearshore processes
DE: 4558 Sediment transport (1862)
SC: Hydrology [H]
MN: 2007 Fall Meeting