Field observations of shear waves in the surf zone
Noyes, T. James
Guza, R. T.
Herbers, T. H. C.
MetadataShow full item record
Alongshore propagating meanders of the mean alongshore current in the surf zone called shear waves have periods of a few minutes and wavelengths of a few hundred meters. Here shear wave properties are estimated with arrays of current meters deployed for 4 months within 300 m of the shoreline of a sandy beach. Shear wave velocity fluctuations are approximately horizontally isotropic, with root mean square values between 10 and 40% of the mean (3-hour-averaged) alongshore current V. Cross-shore variations of the time-averaged shear wave momentum flux are consistent with shear wave energy generation close to shore where the breaking wave-driven mean alongshore current V and current shear Vx are strong and with shear wave energy dissipation and transfer back to the mean flow farther offshore where V and Vx are weak. In case studies where V is a narrow jet near the shoreline the observed strong decay of shear wave energy levels seaward of the jet, and the cross-shore and alongshore structure of shear waves within the jet, are similar to predictions based on the linearly unstable modes of the observed V. Shear wave energy levels also are high in a marginally unstable case with a strong, but weakly sheared, V.
Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 109 (2004): C01031, doi:10.1029/2002JC001761.
Showing items related by title, author, creator and subject.
Thwaites, Fredrik T. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1995-09)This thesis describes the analysis and development of an acoustic vorticity meter to measure shear in ocean-boundary layers over smaller measurement volumes than previously possible. A nonintrusive measurement of vorticity ...
Van Leer, John Cloud (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1971-01)Two shear experiments performed in the permanent thermocline are described and analyzed in this thesis. The first employed dye streak techniques to gain fractional meter vertical resolution. Shears with small vertical ...
Turbulent transport in the outer region of rough-wall open-channel flows : the contribution of large coherent shear stress structures (LC3S) Hurther, D.; Lemmin, U.; Terray, Eugene A. (Cambridge University Press, 2007-02-15)Acoustic Doppler velocity profiler (ADVP) measurements of instantaneous three-dimensional velocity profiles over the entire turbulent boundary layer height, δ, of rough-bed open-channel flows at moderate Reynolds numbers ...