Visual study of variation of flow patterns around a disk in a casing: effects of edge of the disk

This report presents the result of visualization of versatile patterns of flow around a rotating disk in a casing. Investigation of this type of flow has rather long history and many works have been performed from experimental, theoretical and numerical points of views. In this study, we concern the effect of the clearance between a rim wall of a rotating disk and the shroud of the outer casing on the flow structure. The radii of the disks were r_d = 141.8 mm, 135.5 mm, 127.0 mm and 112.0 mm, and the inner radius of a fixed casing is r_e = 142 mm. Flow pattern was visualized using aluminium powder. The Reynolds number based disk radius was varied and its critical value was determined at various bifurcation points. Qualitative structures were determined from time variations of the brightness at fixed pixels of CCD camera used to capture the spiral rolls of flow patterns. The sectional views of clearance space of the disk and the casing unveiled oscillating end flow pattern according to the spiral-roll of plan view.