Skip to Main content Skip to Navigation
Theses

Etude de l'interaction entre le vent et les vagues scélérates

Abstract : The rogue wave phenomenon, which is of majeur interest for marine safety, cannot be correlated to any specific geophysical phenomenon. Such waves can appear on every ocean of the world, in deep or shallow water, and encounter strong winds in tempest zones. This work aims to study the influence of wind on rogue waves. An experimental approach showed that rogue waves generated by means of energy focusing due to the dispersive nature of water waves, were slightly amplified, that there was a drift of the focusing point, and that their life time was significantly increased. A strong asymmetry is indeed observed between the focusing and defocusing stages. Numerical simulations are performed to analyse, understand, and reproduce the phenomenon. Experiments performed in the air-sea interaction facility are reproduced in a numerical wave tank using boundary integrals method. Miles' mechanism and the modified Jeffreys sheltering mechanism are both considered to model wind action. Jeffreys' sheltering mechanism is modified by introducing a threshold in local slope above which air flow separation occurs over steep crests. Rogue waves can also be generated using another physical mechanism : modulationnal instability of wave fields, or Benjamin-Feir instability. An extension of the study to rogue waves due to modulationnal instability is developed. Numerical simulations of this phenomenon are performed with a pseudo-spectral method. These simulations show that the modified Jeffreys' sheltering mechanism is responsible for a significant increase of the lifetime of those extreme waves, such as for rogue waves due to dispersive focusing. However, the underlying physics are different in both cases. However, these approaches are both based on a linear wind wave coupling, neglecting the influence of waves on the air flow, and based on a potential description of the flow. The existence of a recirculation area (air vortex) observed experimentally above the highest crests can only be simulated correctly when vorticity is taken into account. A numerical method to simulate the rotationnal flow of the two phases viscous fluids, separated by an interface, is introduced.
Document type :
Theses
Complete list of metadata

Cited literature [213 references]  Display  Hide  Download

https://tel.archives-ouvertes.fr/tel-00703258
Contributor : Thierry Pin <>
Submitted on : Friday, June 1, 2012 - 12:34:58 PM
Last modification on : Monday, March 29, 2021 - 3:16:03 PM
Long-term archiving on: : Sunday, September 2, 2012 - 2:32:09 AM

File

report-hyperref.pdf
Files produced by the author(s)

Identifiers

  • HAL Id : tel-00703258, version 1

Collections

Citation

Julien Touboul. Etude de l'interaction entre le vent et les vagues scélérates. Océan, Atmosphère. Université de Provence - Aix-Marseille I, 2007. Français. ⟨tel-00703258⟩

Share

Metrics

Record views

1385

Files downloads

3288