HR: 0800h
AN: OS11A-0484    [Abstracts]
TI: Wave Transformation and Undertow Over a Barred Beach
AU: * Fujii, E
EM: efujii@usc.edu
AF: Department of Civil and Environmental Engineering, University of Southern California, Los Angeles, CA 90089-2531 United States
AU: \"{O}zkan-Haller, H
EM: ozkan@coas.oregonstate.edu
AF: College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331-2302 United States
AU: Long, J
EM: jlong@coas.oregonstate.edu
AF: College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331-2302 United States
AB: The mean cross-shore flow (undertow) over a barred beach is examined by calibrating an existing wave and circulation model which will provide predictions that will be compared to in-situ measurements. The wave model applied to the experiment is a linear shoaling model with wave breaking dissipation according to Dally, Dean, and Dalrymple (2002); following the calibration of the wave model the undertow model by Garcez Faria et al. (2000) is calibrated. The experiment was conducted in the long wave flume at the O.H. Hinsdale Wave Research Laboratory at Oregon State University (OSU). Regular waves with a wave height of 0.60 meters and a frequency of 0.25 Hz were generated and vertical velocity profiles were collected at seven different cross-shore locations each with eight to nine points per profile. Three Acoustic Doppler Velocimeters(ADV) were used to collect the cross-shore flow velocities and six fixed wave gauges were used to measure the water surface elevation. The data collected from the wave gauges were processed using a zero-upcrossing analysis followed by ensemble averaging the waves to determine the average wave height of each cross-shore gage. This approach was taken since regular waves are assumed to be similar to one another and would yield higher numbers of realizations, making it a more statistically reliable estimate. In total, 49 different time series were analyzed for each wave gage, yielding a reliable wave height estimate. The calibration of the wave model was accomplished by altering the three free parameters: higher breaking threshold $\gamma$, lower breaking threshold $\gamma$$_{s}$, and an empirical constant $\kappa$, until the wave model best fit the data. Subsequently, the undertow model was calibrated by varying the eddy viscosity ($\mu$) for each profile. The presented work was performed as part of the Research Experience for Undergraduates (REU) program during the summer of 2004 at OSU.
DE: 4500 OCEANOGRAPHY: PHYSICAL
DE: 4512 Currents
DE: 4546 Nearshore processes
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting