Control of thermocapillary instabilities far from threshold

Authors: Brunet, P.B., Amberg, G.A., Alfredsson, P.H.
Document Type: Article
Pubstate: Published
Journal: Phys. Fluids
Volume: 17   104109
Year: 2005


(With G. Amberg and P.H. Alfredsson). We report experiments on control of thermocapillary instabilities at high temperature differences, in an annular geometry. Previous studies (Phys. Fluids \textbf 3039-3045 (2002)) showed that a reasonable control of oscillatory instability could be achieved by optimizing a local heating feed-back process. We conducted experiments with a basic flow converging from periphery to center. This constitutes a more unstable configuration than previously, and enables appearance of higher-order instabilities and chaos. Applying successfully local feedback control to the periodic state close to the threshold, we extend the process to higher temperature differences, where non-linear as well as proportional/derivative control laws are necessary to obtain a significant decrease of the temperature fluctuations. Finally, proportional control allows us to synchronize a chaotic state, to a periodic one.