We report experiments on control of thermocapillary instabilities at high temperature differences, in an annular geometry. Previous studies ͓Phys. Fluids 14, 3039 ͑2002͔͒ showed that a reasonable control of oscillatory instability could be achieved by optimizing a local heating feedback 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

more »

... aos. Applying successfully local feedback control to the periodic state close to the threshold, we extend the process to higher temperature differences, where nonlinear 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.