Transition of the Flow around the Rotating Disk with a Radial Gap in a Cylindrical Casing with Increasing of the Reynolds Number

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The flow around a rotating disk in a cylindrical casing is investigated by the numerical method. The radius of the disk is shorter than the inner radius of the casing, as well as the thickness of the disk is smaller than the axial length of the casing. Therefore, the flow field has a radial gap in addition to an axial gap. When there is an axial gap, the flow has been regarded as the cross flow model, and the spiral rolls and spots appear in the Bödewadt layer on the stationary end wall of the casing. Taylor-Couette vortices emerge in the radial gap by the influences of the rotating disk with finite thickness and the side wall of the casing. This results in the generation of the flow with bead-like and sickle-like vortices near the radial gap. We visualize the flow and investigate the appearance and the collapse of bead-like vortices. We also show the transition process of the flows that depend on the Reynolds number. In the transition process with increasing Reynolds number, we can find Taylor vortex flow, flow with bead-like vortices, sickle-like vortices and the spiral rolls. It is shown that the sickle-like vortices is generated only in the case where bead-like vortices is biased to one side of the casing end walls and gives the fluctuation to generate energy and torque.