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| Titel |
Nonlinear reflection of internal gravity wave onto a slope |
| VerfasserIn |
Keshav Raja, Joel Sommeria, Chantal Staquet, Matthieu Leclair, Nicolas Grisouard, Louis Gostiaux |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250133043
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| Publikation (Nr.) |
 EGU/EGU2016-13612.pdf |
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| Zusammenfassung |
| The interaction of internal waves on sloping topography is one of the processes that cause
mixing and transport in oceans. The mixing caused by internal waves is considered to be an
important source of energy that is needed to bring back deep, dense water from the abyss to
the surface of the ocean, across constant density surfaces. Apart from the vertical transport of
heat (downwards) and mass (upwards), internal waves are also observed to irreversibly
induce a mean horizontal flow. Mixing and wave induced mean flow may be considered
as the processes that transfer wave induced energy to smaller and larger scales
respectively. The process of mixing has been a subject of intense research lately. However,
the process of wave induced mean flow and their dynamic impact await thorough
study. The present study involves this wave induced mean flow, its generation and
energetics.
The nonlinear subcritical reflection of internal waves from a sloping boundary is studied
using laboratory experiments carried out on the Coriolis Platform at Grenoble and, 2D and
3D numerical simulations done using a non-hydrostatic code. In the experiment, a plane wave
is produced using a wave generator and is made to reflect normally on a sloping bottom in a
uniformly stratified fluid. We consider both rotating and non-rotating cases. The numerical
simulation mimicks the laboratory setup with an initial condition of an analytical plane wave
solution in a vertical plane limited by a smooth envelope to simulate the finite wave
generator.
The interaction of the incident and reflected waves produce, apart from higher harmonics,
an irreversible wave induced mean flow which grows in time and is localised in the
interacting region. The finite extent of the wave generator allows the mean flow to recirculate
in the horizontal plane, resulting in a dipolar potential vorticity field. Moreover,
the generation of mean flow and higher harmonics, along with dissipative effects,
diminishes the amplitude of reflected wave. We study the momentum and energy
budget of the process in order to understand the mechanism of generation of mean
flow, its interaction with the wave and account for the loss of wave energy upon
reflection.
REFERENCES
N. Grisouard, M. Leclair, L. Gostiaux and C. Staquet 2013. Large scale energy transfer from
an internal gravity wave reflecting on a simple slope IUTAM Symposium Procedia 8
119-128
M. Leclair, K. Raja and C. Staquet 2016. Nonlinear reflection of a two-dimensional
finite-width internal gravity wave onto a slope Journal of Fluid Mechanics. in preparation |
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