Spin coating has been extensively investigated. However, a numerical study of the wind shear effect on film thickness distributions over doughnut disks has not yet been performed. Also, the effect of a hub on the air shear flow over a rotating doughnut disk has not yet been addressed. In this study, we predict successive liquid surface contours on rotating doughnut disks. The results are compared with experimental data, and discrepancies between them are identified. We found that the discrepancies are caused mainly by the presence of a hub, and that the wind shear effect cannot be simply analyzed in terms of Cochran's solution.
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JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS