Münster 1999 – scientific programme

Parts | Days | Selection | Search | Downloads | Help

DY: Dynamik und Statistische Physik

DY 34: Hydrodynamik

DY 34.5: Talk

Wednesday, March 24, 1999, 15:45–16:00, R4

Thee-dimensional simulations of Bénard-Marangoni convection at small Prandtl number — •Th. Boeck¹ and A. Thess^2,1 — ¹Institut f"ur Luft– und Raumfahrttechnik, TU Dresden, 01062 Dresden — ²Fakult"at Maschinenbau, TU Ilmenau, PF 100565, 98684 Ilmenau

The quiescent state in a fluid layer with a free upper surface heated from below can become unstable due to the temperature dependence of the surface tension (Marangoni effect). Self-sustaining convection occurs when the heat flux imposed across the layer exceeds a certain critical value. We investigate the convective flow in the limit of small Prandtl number in a small-aspect-ratio domain using three-dimensional numerical simulations with a pseudo-spectral Fourier-Chebyshev method. Upon increasing the heating we first observe hexagonal convection cells which become quickly unstable with respect to more complex flow patterns. The flow becomes time-dependent when the heat flux is only about 20% larger than at the linear stability threshold of convection. The phenomenon of inertial convection observed in the two-dimensional case [1] is not present in three dimensions, but the flywheel effect underlying the transition to inertial convection is still noticeable. It gives rise to an intermittent flow characterized by phases of two-dimensionalization with exponential growth of the flow amplitude followed by a breakdown due to three-dimensional perturbations.

[1] T. Boeck, A. Thess, J. Fluid Mech. 350, 149 (1997).