Berlin 2012 – wissenschaftliches Programm
DY 16.1: Topical Talk
Mittwoch, 28. März 2012, 10:00–10:30, MA 144
Pepsi®–or ◯̴ interfacial instabilities between magnetic/non-magnetic liquids — •Reinhard Richter — Experimentalphysik 5, Universität Bayreuth
Turn a can upside down and lift the pull-tab! The heavier liquid will start to leave the vessel through the small orifice, whereas air tries to enter it from below. This unstable condition is known as Rayleigh-Taylor instability. For magnetic beverages it may become stable by applying a rotating magnetic field, oriented parallel to the flat interface . We present a first experimental confirmation  of this prediction and measure the shape of the interface for different magnetic fields utilizing radioscopy .
On the contrary, a magnetic liquid layer will become unstable if the field is oriented normally to the interface, and a critical field strength is surpassed. The resulting Rosensweig instability is measured in a highly viscous ferrofluid via a sequence of magnetic pulses. This allows us to catch the phase space dynamics, and to reconstruct the underlying fully nonlinear equation of motion of the pattern amplitude . When exploring the control parameter-phase space, localized states are uncovered next to the unstable branch of the bifurcation diagram.
 D. Rannacher and A. Engel, Phys. Rev. E 75, 016311 (2007).  A. Poehlmann, Diplomarbeit, Universität Bayreuth (2011).  R. Richter and J. Bläsing, Rev. Sci. Instrum. 72, 1729 (2001).  C. Gollwitzer, I. Rehberg, and R. Richter, New J. Phys. 12, 093037 (2010).