HR: 0800h
AN: OS21B-1216    [Abstracts]
TI: Modeling Sheet Flow in Oscillatory Flows Using a Mixture Approach
AU: * Burdick, G M
EM: burdick@coastal.ufl.edu
AF: Department of Civil and Coastal Engineering, University of Florida PO Box 116580, Gainesville, FL 32611-6580 United States
AU: Slinn, D N
EM: slinn@coastal.ufl.edu
AF: Department of Civil and Coastal Engineering, University of Florida PO Box 116580, Gainesville, FL 32611-6580 United States
AB: Understanding the transport of sediment is crucial to predicting many coastal engineering processes, such as sedimentation and erosion around structures and beach profile changes. Traditional methods for modeling sediment transport require solving separate equations for fluid and particle motion. For densely-laden flows, this can present challenges in capturing the physics of the system, as fluid-particle and particle-particle interactions must be accounted for, and can present difficulties because of the computational effort required. In this approach, fluid-particle interactions are expressed through the drag and lift forces, while adequate models for particle-particle interactions are currently being developed. We have chosen an alternate approach that assumes a system containing sediment particles can be approximated as a mixture having variable density and viscosity that depend on the local sediment concentration. Here, the interactions are expressed through the mixture viscosity and a stress-induced diffusion term. There are five governing equations that describe the flow field. They are the mixture continuity and momentum equations and a species continuity equation for the sediment. We use the control volume approach on a three-dimensional staggered grid to solve the equations numerically. The turbulent dynamics of an initially stationary densely packed sand layer (60% by volume sand) driven by a sinusoidally oscillating flow are examined and model results are compared with the experimental data of Horikawa, Watanabe, & Katori (1982). The model does a reasonable job of predicting concentration profiles and sheet flow layer thickness. Both the model and the experimental data show that a significant amount of sand is entrained during the acceleration phase of the wave cycle. This entrained sand then falls back to the bed during the deceleration phase of the wave cycle.
DE: 4546 Nearshore processes
DE: 4558 Sediment transport
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting