The effect of viscosity on rupture dynamics in the non-uniformly heated horizontal liquid film

In the present work, we study the rupture dynamics of a horizontal liquid film non-uniformly heated from below in a wide range of liquid viscosity. To visualize the liquid surface deformations and disruption of the film, we use a Nikon digital camera (shot at 60 fps) coupled with an optical schlieren system. In order to measure the instantaneous film thickness, we use the confocal Micro-Epsilon chromatic sensor. It was found that the process of film rupture can be divided into three stages: 1) film thinning down to a residual film on the heater; 2) existence of a stable residual film for some time; 3) rupture and dryout of the residual film. The thickness of the residual film was found to strongly depend on the liquid viscosity: For water, it is about 10 μm, whereas for PMS-200 it is about 275 μm.