The Counter-propagating Rossby Waves' perspective to shear flows
Event details
| Date | 26.09.2013 |
| Hour | 10:00 › 12:00 |
| Speaker | Prof. Eyal Heifetz, Tel Aviv University |
| Location | |
| Category | Conferences - Seminars |
The concept of Counter-propagating Rossby Waves (CRWs) was been introduced by Bretherton (1966) to explain the basic mechanism of baroclinic instability in the atmosphere. This is the main mechanism which generates cyclones and hence determines the weather in the mid-latitudes. CRWs are vorticity waves which propagate in regions of strong vorticity gradients in a counter-direction to the mean flow (the mid-latitudinal atmospheric jet ). They interact in a distance by inducing a far velocity field which enables them to be phase-locked in a growing configuration.
In this talk I will try to relate this approach to general shear flow instability and to show how it rationalizes different fundamental aspects of the instability including the necessary conditions for the onset of the instability, and the mechanism of optimal non-normal growth and how it feeds back with nonlinear mixing.
Finally, I will suggest a more general type of modified Rossby-gravity wave instability in the presence of stratification, where the dynamics is formulated solely in terms of vorticity and wave displacement across the shear. I will argue that the latter formulation can be generally applied to various different setups where external forces generate vorticity by exerting torque on the flow.
In this talk I will try to relate this approach to general shear flow instability and to show how it rationalizes different fundamental aspects of the instability including the necessary conditions for the onset of the instability, and the mechanism of optimal non-normal growth and how it feeds back with nonlinear mixing.
Finally, I will suggest a more general type of modified Rossby-gravity wave instability in the presence of stratification, where the dynamics is formulated solely in terms of vorticity and wave displacement across the shear. I will argue that the latter formulation can be generally applied to various different setups where external forces generate vorticity by exerting torque on the flow.
Practical information
- General public
- Free
Organizer
- the laboratory of Fluid Mechanics and Instabilities (LFMI)
Contact
- Prof. François Gallaire