DREANO ROESCH, M Théo (2024) The downstream development of a baroclinic instability in an open channel PRE - Research Project, ENSTA.

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Abstract

The downstream development of a baroclinic instability in an open channel is explored through a combination of theoretical analysis and numerical simulations. The model used in this report is a two-layer quasi-geostrophic model without beta-effect. The study focuses on the influence of the shear which deeply changes the behavior of the motion. In a crescendo fashion, the report delves into three cases: linear, weakly nonlinear, and fully nonlinear. First, it outlines the conditions for temporal and spatial instability. Then, the weakly nonlinear theory is studied through numerical modeling with the pseudo-spectral method. The number of vertical modes computed in the simulation is revealed to be crucial. Two vertical modes are enough to observe the structure of the instability, yet the higher modes represent a nonnegligible part of the energy. When progressively shifting to a turbulent regime, the modes begin to work in pairs in terms of energy. Finally, it exposes the boundary between weakly nonlinear and turbulent regimes, offering a foundation for further study into the chaotic behavior of the motion.

Item Type:Thesis (PRE - Research Project)
Uncontrolled Keywords:baroclinity, quasi-geostrophic, weakly nonlinear, instability, modal analysis
Subjects:Earth Sciences and Environmental Engineering
Fluid Mechanics and Energy
ID Code:10132
Deposited By:Théo DREANO--ROESCH
Deposited On:28 août 2024 15:49
Dernière modification:28 août 2024 15:49

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