摘要(英) |
The effect of Coriolis force on the rivulet (fingering) instability, the onset of rivulet phenomena during spin coating, is investigated by flow visualization experiments incorporating with dimensional analysis. And a scaling law is provided to discover the forces relation during coating process. This study demonstrates that the Coriolis force do affect significantly the critical radius of rivulet instability, the deflection angle of instability rivulet and the maximum attainable radius of the coating films. From the onset of the effect of Coriolis force, the finger’s deflection angle increases rapidly with rotational Reynolds number Reω. The strongest effect of Coriolis force is seen to appear while the film height is closed to the Ekman boundary layer. For the cases of low Bond number, the effect of Coriolis force is a stabilizing factor, and the dimensionless critical radius increases slightly with increasing Reω. The finger’s base area develops into a triangular-like shape due to the changing of finger’s deflected angle. It results in the merging together of fingers, which in turn leads to the increase of maximum attainable radius. Finally, the scaling law successful provides several characteristic length scales which are balanced by the Coriolis force with the surface tension and the viscous force with the surface tension. |
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