| Τύπος: |
Διάλεξη |
| Ημ/νία Έναρξης: |
3/12/2009 |
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| Ώρα Έναρξης: |
13:00 |
| Ώρα Λήξης: |
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| Ομιλητής: |
Dr. Judith Vateville, Post Doctoral Researcher, University of Thessaly |
| Τίτλος: |
Investigation of the dynamics of very viscous thermal plumes in the lab-Application to Earth's mantle plumes |
| Περιγραφή: |
In Earth Sciences, hot upwelling plumes are thought to develop from the base of the 2900 km-thick solid mantle of our planet and to generate hotspots, i.e. intraplate volcanic islands such as Hawaii and La Reunion. Although generated through chaotic Rayleigh-Benard instabilities at a high Prandtl number, they can be modelled with the simpler case of starting plumes out of a finite-size heater, either numerically for infinite Prandtl number, or in the laboratory with very viscous fluids. Hence, the question is to find simple scaling laws for isolated rising plumes and apply them to the Earth's mantle case. In this presentation we investigate the characteristics of an isolated plume growing in a viscous fluid. We use both laboratory experiments and numerical models : the visualization techniques give us access to the growing plume temperature and velocity fields, on a 2-D section of the tank, whereas the numerical simulations are axisymmetric finite element simulations that attempt to reproduce the laboratory conditions as closely as possible. We find excellent quantitative agreement between the two fully independent approaches. This issued to derive scaling laws for the dynamics of the plume head and stem, and apply them to the Earth's case. We further show that confinement effects are more important than inertial effects and consequently that plumes dynamics are well described by the approximation of infinite Prandtl number.
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| Χώρος: |
Αίθουσα Συνεδριάσεων |
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