Abstract

We present experimental results for early transients near the onset of convection of an ethanol-water mixture in cylindrical containers heated from below. The separation ratio of the mixture was ψ≈− 0. 0 8, and the aspect ratios Γ≡ r/d (r is the radius and d the height of the sample cell) of two different containers were 10.91 and 11.53. For this system the onset of convection occurs via a subcritical Hopf bifurcation to traveling waves. Beyond the bifurcation we found transient radially traveling waves whose amplitude grew in time. We decomposed the transient patterns into azimuthal modes of the form cos m θ. The azimuthal symmetry of the pattern depended strongly on Γ. For Γ= 10.91 odd azimuthal modes were preferred, while for Γ= 11.53 even modes dominated. We measured the spatial and temporal growth rates at various ε≡ Δ T/Δ T c− 1 for different azimuthal modes and compared the results for the two aspect …

Date

March 1, 1999

Authors

Kristina Lerman, David S Cannell, Guenter Ahlers

Journal

Physical Review E

Volume

59

Issue

3

Pages

2975

Publisher

American Physical Society