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Title:
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Frontshear and backshear instabilities of the mean longshore current
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Author:
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Baquerizo, Asunción; Caballeria, Miquel; Losada, Miguel A.; Falqués, Albert
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Other authors:
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Universitat de Vic. Escola Politècnica Superior; Universitat de Vic. Grup de Recerca en Medi Ambient i Alimentació |
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Notes:
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An analytical model based on Bowen and Holman [1989] is used to prove the
existence of instabilities due to the presence of a second extremum of the background
vorticity at the front side of the longshore current. The growth rate of the so-called
frontshear waves depends primarily upon the frontshear but also upon the backshear and
the maximum and the width of the current. Depending on the values of these parameters,
either the frontshear or the backshear instabilities may dominate. Both types of waves
have a cross-shore extension of the order of the width of the current, but the frontshear
modes are localized closer to the coast than are the backshear modes. Moreover, under
certain conditions both unstable waves have similar growth rates with close wave numbers
and angular frequencies, leading to the possibility of having modulated shear waves in the
alongshore direction. Numerical analysis performed on realistic current profiles confirm
the behavior anticipated by the analytical model. The theory has been applied to a current
profile fitted to data measured during the 1980 Nearshore Sediment Transport Studies
experiment at Leadbetter Beach that has an extremum of background vorticity at the front
side of the current. In this case and in agreement with field observations, the model
predicts instability, whereas the theory based only on backshear instability fai led to do so. |
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Subject(s):
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-Oceanografia
-Geofísica |
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Rights:
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(c) American Geophysical Union, 2001
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Document type:
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Article
Article - Published version |
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Published by:
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American Geophysical Union
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