Switching between different types of stability isles in films over topographies
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In the present study, we performed comprehensive experiments and direct Navier–Stokes computations on the linear stability of gravity-driven film flows. We focused on the switching between different types of stability isles, appearing in viscous films over inclined topographies, which describes an abrupt change of the flow’s free-surface stability. We systematically varied the inclination angle, the liquid, the substrate’s shape and the corrugation’s periodicity and uncovered when this phenomenon appears and how it proceeds. Our combined experimental and numerical work unveiled that the switching is of a universal nature as it can be induced by a slight variation of one of the multitude of completely differing parameters mentioned above. The in-depth investigation of this phenomenon presented in this article is of interest for the technical exploitation of film flows as it puts the reader into the position to avoid high-risk situations where a small change of the system’s configuration leads to a significantly different system response.
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We wish to thank Marion Märkl, Stephan Eißner and Dominik Schröder for their help in carrying out parts of the experiments and kindly acknowledge the DAAD for providing a visiting fellowship for Prof. Trifonov, Grant No. 91577374, which made this project possible.
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