In order to investigate the effects of the cone-shaped bottom of a rotating cylinder on spin-up, experiments were performed and Homicz & Gerber model was modified. The depth of the rotating cylinder changes linearly along the radial position. Flow field was visualized by means of aluminium flakes. The position of shear front and the transient shape of free surface were measured by Image Processing techniques. The thickness of Ekman layer on an inclined bottom changes along the radial position showing thicker Ekman layer at deeper position. Flux through the inclined Ekman layer is nearly the same as flux through a corresponding flat Ekman layer. Shear front moves faster inward in the shallow region of the cylinder than in the deep region. Spin-up of a fluid in the cylinder with a coneshaped bottom was accomplished faster than a corresponding flat bottom. Difference in depth of rotating cylinder is the main cause of the change in spin-up process. This trend comes out in the progressing shapes of free surface. Modified Homicz & Gerber model shows similar trend. In the present geometry, spin-up was little influenced by the change of Reynolds number, but influenced significantly by the change of aspect ratio. The effects become larger for smaller aspect ratio.
