Inertia-gravity-wave generation: a geometric-optics approach

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Inertia-gravity-wave generation: a geometric-optics approach's image

Description:	Vanneste, J (Edinburgh) Wednesday 10 December 2008, 10:00-10:30

Created:

2009-01-15 15:17

Collection:

The Nature of High Reynolds Number Turbulence

Publisher:

Isaac Newton Institute

Vanneste, J

Language:

eng (English)

Credits:

Author:

Vanneste, J


Abstract:	The generation of inertia-gravity waves in complex flows is examined using a geometric-optics approach. This approach considers the dynamics of a small-scale wavepacket in prescribed time-dependent, balanced flow. The wavepacket is assumed to be in the so called wave-capture regime, where the wave intrinsic frequency is negligible compared with the Doppler shift. The dynamics is reduced to a number of ordinary differential equations describing the evolution of the wavepacket position, of the wavevector, and of three scalar fields describing the wavepacket amplitude and polarisation. The approach clearly identifies two classes of wave-generation processes: unbalanced instabilities, associated with linear interactions between inertia-gravity waves, and spontaneous generation, associated with a conversion between vortical and inertia-gravity modes. Applications to idealised and realistic flows are discussed. A seminar from the Rotating Stratified Turbulence and Turbulence in the Atmosphere and Oceans conference in association with the Newton Institute programme: The Nature of High Reynolds Number Turbulence www.newton.ac.uk/programmes/HRT/seminars/

Abstract:

The generation of inertia-gravity waves in complex flows is examined using a geometric-optics approach. This approach considers the dynamics of a small-scale wavepacket in prescribed time-dependent, balanced flow. The wavepacket is assumed to be in the so called wave-capture regime, where the wave intrinsic frequency is negligible compared with the Doppler shift. The dynamics is reduced to a number of ordinary differential equations describing the evolution of the wavepacket position, of the wavevector, and of three scalar fields describing the wavepacket amplitude and polarisation. The approach clearly identifies two classes of wave-generation processes: unbalanced instabilities, associated with linear interactions between inertia-gravity waves, and spontaneous generation, associated with a conversion between vortical and inertia-gravity modes. Applications to idealised and realistic flows are discussed.

A seminar from the Rotating Stratified Turbulence and Turbulence in the Atmosphere and Oceans conference in association with the Newton Institute programme: The Nature of High Reynolds Number Turbulence
www.newton.ac.uk/programmes/HRT/seminars/

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