Instabilities in the flow of thin films on heterogeneous surfaces

We present computational and experimental results involving instability development in the gravity-driven flow of thin fluid films on heterogeneous surfaces, with particular emphasis on the dynamics of the fluid fronts. We show that heterogeneity of the solid surface can have a significant effect on the flow dynamics. Since the effect of heterogeneity often competes with the basic instability mechanism that would occur even on macroscopically homogeneous surfaces, the result is an elaborate interplay of various instability mechanisms. The computational results presented here outline both the flow on surfaces perturbed by regular patterns, and on surfaces perturbed by irregular, noiselike perturbations. We relate these computational results to the pattern formation process in our experiments of gravity-driven flow down an incline. Good qualitative agreement is found between the simulations and the experiments. © 2004 American Institute of Physics. [DOI: 10.1063/1.1772732]