Dresden 2011 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 40: Posters II

DY 40.12: Poster

Donnerstag, 17. März 2011, 17:00–19:00, P3

Spatially Modulated Thermal Convection — •Georg Freund, Werner Pesch, and Walter Zimmermann — Theoretische Physik I, Universität Bayreuth, 95440 Bayreuth

We study Rayleigh-Bénard convection (RBC) in a horizontal fluid layer heated from below and investigate theoretically different methods of imposing spatially periodic modulations.

It is well known that in (unmodulated) RBC a purely conductive state becomes unstable to convection, when the applied temperature gradient exceeds a critical value. The presence of spatial modulations breaks the translational symmetry leading to a convective state for any finite temperature difference between the top and bottom boundary. The spatial variation of such a ‘forced’ state follows the imposed modulation. However, these forced rolls are only stable for overcritical temperature gradients, if the wavenumber of the modulation lies in the vicinity of the critical wavenumber of unmodulated RBC. In this case one finds an imperfect-bifurcation scenario.

In recent experiments spatial modulations have been imposed by gluing block-shaped polymer stripes onto the lower boundary plate, while theoretical treatments exist for spatially varying temperature conditions on geometrically flat and to some extent on wavy-shaped boundary plates.

We solve the Oberbeck-Boussinesq equations directly and compare the various types of boundary conditions with each other. This allows for the first time a quantitatively consistent comparison to the experimental results.