HR: 0800h
AN: OS21B-1236    [Abstracts]
TI: Evaluation of Wave-Current Bottom Boundary Layer Models
AU: * Nichols, C S
EM: nichols.236@osu.edu
AF: Ohio State University, 470 Hitchcock Hall, 2070 Neil Ave, Columbus, OH 43210-1275 United States
AU: Foster, D L
EM: foster.316@osu.edu
AF: Ohio State University, 470 Hitchcock Hall, 2070 Neil Ave, Columbus, OH 43210-1275 United States
AU: Sherwood, C R
EM: csherwood@usgs.gov
AF: U. S. Geological Survey, Coastal and Marine Geology, 384 Woods Hole Road, Woods Hole, MA 02543-1598 United States
AU: Warner, J
EM: jcwarner@usgs.gov
AF: U. S. Geological Survey, Coastal and Marine Geology, 384 Woods Hole Road, Woods Hole, MA 02543-1598 United States
AB: Recent advances in flow and sediment transport modeling have allowed for the simulation of wave-current bottom boundary layers and the resulting sediment transport for a range of observed flow and topographic conditions. An example of this is a non-hydrostatic numerical model, Dune, which resolves the relevant dynamics of wave and current boundary layers over smooth and rough movable sand beds and includes multiple bed load and suspended load transport models (Tjerry, 1995). In the quasi-three dimensional version of Dune, the morphology and forcing is assumed to be uniform in the alongshore direction allowing the alongshore momentum equation to be treated as a transport equation. In our investigations, the established physics have been maintained and the forcing and boundary conditions have been modified, so that the model may be compared directly with field observations. The model has been evaluated with Acoustic Doppler Profiler observations made in several meters of water over both flat and rippled beds. Model-data comparisons of both the mean and oscillatory bottom boundary layers have been favorable for both flat and rippled beds. In this presentation, we use the above model to evaluate the Grant and Madsen (1994) wave-current bottom boundary layer model for a range of flow and topographic conditions. Wave-current bottom boundary layer models, such as Grant and Madsen, are used for the parameterization of the mean friction velocity and apparent bottom roughness in larger scale circulation models. Model comparisons are performed for both flat and rippled beds during occasions of both small and large mean current forcing. Model-model comparisons are performed on vertical profiles of the mean horizontal velocity and the eddy viscosity. We specifically examine the sensitivity of the mean flow to both the wave and topographic induced roughness. In addition to providing the opportunity for model evaluations over a wider array of forcing conditions, this investigation may improve the sub-grid scale parameterizations required for larger scale coastal sediment transport models.
DE: 4546 Nearshore processes
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting