HR: 0800h
AN: OS41A-0173    [Abstracts]
TI: On the instability leading to rip currents due to wave-current interaction
AU: * Yu, J
EM: jie_yu@ncsu.edu
AF: North Carolina State University Jie Yu, Civil, Construction and Environmental Engineering Campus Box 7908, Raleigh, NC 27695, United States
AB: We re-examine the hydrodynamic instability due to wave-current interaction and leading to the formation of rip currents (i.e. nearshore circulations) on beaches which are alongshore uniform. Attention is restricted to normally incident waves and the region inside, and just offshore of, the surf zone where linearized shallow water waves are applied. The coupling of waves and circulations is modelled using the concept of wave radiation stresses and the classical ray theory. It is shown that when the fully dynamical interactions of waves and currents are duly accounted for, and proper mathematical analysis is carried out, the instability not only exists, but also leads to rip currents with scales comparable to field observations. The instability properties, in terms of the neutral modes, the most unstable mode and the corresponding maximum growth rate, are examined in the domain of parameters which represent the effects of offshore wave height and bottom friction dissipation. Comparisons with observations of natural rip currents are made, and qualitative agreements are achieved.
DE: 3215 Instability analysis
DE: 3285 Wave propagation (0689, 2487, 4275, 4455, 6934)
DE: 4217 Coastal processes
DE: 4534 Hydrodynamic modeling
DE: 4536 Hydrography and tracers
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting