Effects of Fluid Accelerations on Sediment Transport in Surf Zones

by Daniel T. Cox, Univ of Delaware, Newark, United States,
Nobuhisa Kobayashi, Univ of Delaware, Newark, United States,
Hajime Mase, Univ of Delaware, Newark, United States,

Document Type: Proceeding Paper

Part of: Coastal Sediments


Two hydraulic model tests were run in a wave flume using irregular waves to obtain detailed data on the cross-shore variations of the pressure gradient on a 1:20 smooth, impermeable slope. The data was analyzed using the simple criterion of the momentary failure proposed by Madsen (1974). The occurrence probability of the momentary landward and seaward failure of a porous sand bed was estimated to be the largest in the inner surf zone where the pressure fluctuations caused by wave breaking reached the bottom. In addition, the measured pressure gradients were used to estimate the Lagrangian fluid acceleration near the bottom and the resulting inertia force acting on a sediment particle. The inertia force was predicted to be on the order of the submerged weight of the particle and secondary compared to the drag force acting on the particle even in the surf zone.

Subject Headings: Sediment transport | Surf zones | Breaking waves | Hydraulic models | Fluid flow | Water waves | Wave pressure | Drag (fluid dynamics)

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