Suppression of eddies in films over topography

We study inertial film flow down undulated inclines With increasing Reynolds number, eddies are formed in the troughs of the bottom undulation Further increase leads to a diminution of the eddies until they vanish completely At even higher Reynolds numbers, they reappear yielding an eddy-free window of Reynolds numbers Within this window, the free-surface shape changes abruptly The change comes along with a sudden decrease in the mean film thickness and an abrupt transition of the surface shape type from anharmonic with a strong indentation to harmonic The anharmonic surface shape shows typical features of a hydraulic jump, which vanishes during the transition We find that the eddies disappear at Reynolds numbers where the first harmonic of the free-surface contour is sufficiently strong regardless of the exact surface shape Numerical calculations are in good agreement with the experimental findings (C) 2010 American Institute of Physics [doi 10 1063/1 3504374]