Berkeley Fluids Seminar
University of California, Berkeley
Bring your lunch and enjoy learning about fluids!
September 25, 2013
Prof. Hubert Klahr (Max Planck Institut für Astronomie, Germany)
Stability of Rotating Fluids or What makes Circumstellar Disks form Vortices
Gas disks around young stars are known to be unstable to some unknown process, because there is evidence for mass accretion onto the star, which creates the necessity for a hi gh efficient most likely turbulent viscosity. Magnetic fields can do this job in the ionized dense inner parts of this disks. But for regions basically beyond todays orbit of Earth gas is too co ld and too full of dust grains, which absorb all free electrons. These regions, typically coined Dead-Zones are the playground for a bunch of possible hydrodynamic instabilities which I will rev iew in this presentation. Especially the fact that the disks have a finite thermal relaxation time on the order of the orbital period is discussed in a stability analysis for stratified disks. Then the occurrence of a convective over-stability (following the terminology of Chandrasekhar) can be shown, leading to the formation and amplification of vortices.