Low-mode internal tide generation by topography: an experimental and numerical investigation

We analyse the low-mode structure of internal tides generated in laboratory experiments and numerical simulations by a two-dimensional ridge in a channel of finite depth. The height of the ridge is approximately half of the channel depth and the regimes considered span sub- to supercritical topograp...

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Bibliographic Details
Published in:Journal of fluid mechanics 2009-10, Vol.636, p.91-108
Main Authors: ECHEVERRI, PAULA, FLYNN, M. R., WINTERS, KRAIG B., PEACOCK, THOMAS
Format: Article
Language:English
Subjects:
Dynamics of the ocean (upper and deep oceans)
Earth, ocean, space
Energy conversion
Exact sciences and technology
Experiments
External geophysics
Fluid dynamics
Fluid mechanics
Mathematical models
Physics of the oceans
Ridges
Theory
Tides
Topography
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Summary:We analyse the low-mode structure of internal tides generated in laboratory experiments and numerical simulations by a two-dimensional ridge in a channel of finite depth. The height of the ridge is approximately half of the channel depth and the regimes considered span sub- to supercritical topography. For small tidal excursions, of the order of 1% of the topographic width, our results agree well with linear theory. For larger tidal excursions, up to 15% of the topographic width, we find that the scaled mode 1 conversion rate decreases by less than 15%, in spite of nonlinear phenomena that break down the familiar wave-beam structure and generate harmonics and inter-harmonics. Modes two and three, however, are more strongly affected. For this topographic configuration, most of the linear baroclinic energy flux is associated with the mode 1 tide, so our experiments reveal that nonlinear behaviour does not significantly affect the barotropic to baroclinic energy conversion in this regime, which is relevant to large-scale ocean ridges. This may not be the case, however, for smaller scale ridges that generate a response dominated by higher modes.
ISSN:0022-1120
1469-7645
DOI:10.1017/S0022112009007654