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ISSN Online: 2377-424X

ISBN Print: 1-56032-797-9

International Heat Transfer Conference 11
August, 23-28, 1998, Kyongju, Korea

EXPERIMENTAL OBSERVATION OF THREE-DIMENSIONAL WAVE EVOLUTION ON A FALLING LIQUID FILM

Get access (open in a dialog) DOI: 10.1615/IHTC11.830
pages 177-182

Аннотация

Surface waves separated well from each other (solitary waves) were excited on a water film falling down a vertical surface by introducing controlled temporal disturbances of constant frequencies into the film entrance, and the response of the waves to spatial disturbances generated by perturbations located just below the film entrance is analyzed. The results show that the two-dimensional waves of small phase velocities are unstable to spatial disturbances of large wavelengths and transform into three-dimensional waves having sinusoidal wave fronts, while the waves of intermediate and large phase velocities are unstable to small wavelength disturbances and their wave fronts bend to form several U-shapes on each front. The U-shapes (or 'U's) originate from the perturbations, and they align in a row with the corresponding perturbations. When a single perturbation is put on the film, a 'U' originating from the perturbation leads to the generation of a new 'U' on either side, i.e. a self-induced lateral propagation occurs.
It is pointed out that these surface waves hold vortices occurring in a shear layer bounded by a solid surface and a free liquid-gas interface, and the U-shaped waves resemble both the A-vortices and horseshoe-shaped vortices observed in boundary layers on walls