Two dimensional hydrothermal waves in an extended cylindrical vessel

We report experimental results for hydrothermal waves instability in thermo capillary-driven flow in an extended cylindrical geometry. The waves are sh own to appear via a supercritical I-o instability. At larger fluid depth, t he conventional predictions of Smith and Davis - planar waves referred to a s HW1 - are observed. For smaller depth, i.e. for larger aspect ratios, a n ew kind of spatial behavior is reported which may be interpreted as a new i nstability. This new instability is localized in the center of the cell and its spatial structure close to onset resembles targets, i.e. purely radial waves. We refer to these hydrothermal waves as HW2.