The effect of rim-shroud gap on the spiral rolls formed around a rotating disk

Abstract

In this paper, we use the numerical and empirical approaches and investigate the flow around a finite size disk in a finite size outer cylindrical casing. The disk is located at the center of the stationary casing and it is supported by a driving shaft through the disk and the casing. The disk rotates with the driving shaft. Five sizes of disks with different thicknesses and radii are used. The main purpose of this paper is to estimate the effect of the radial gaps on the entire flows. The combination of the thickness of the disk with smaller radius and the inner side of the casing with larger radius forms Taylor–Couette-like vortex flow in the radial gap. The supercritical instability makes the unsteady wavy vortex flow around the disk rim. When the axial gap between the disk surface and the end-wall of the casing is wide, the unsteady wavy flow is convected along the end-wall of the casing and it makes spiral rolls with negative front angles. When the axial gap is narrower and the Reynolds number is small, the instabilities are confined in the radial gap, and a beadlike flow appears around the disk rim. At higher Reynolds number, the turbulent spirals and the mixed spirals with positive and negative front angles are predicted. It is also shown that the phase velocity of the spiral is about or above the half of the velocity of the rotating disk.

Effect of Axial Clearance on the Flow Structure around a Rotating Disk Enclosed in a Cylindrical Casing

“…At the higher Reynolds number, the flow has spiral structures around the disk tip. Some of the flow patterns such as the bead-like flow and the polygonal flow are also found in our experimental investigations [19] [20]. However, the transition mechanism is still unclear and it is one of the future studies.…”

“…This means, even in the flow around a rotating disk, the end-wall effect on the onset and the development of Taylor vortices is one of the interesting topics of this flow. Watanabe and Furukawa [19] [20] numerically and experimentally investigated the flow around a rotating disk confined in a cylindrical casing. The disk driven by a thin shaft is settled at the center of the casing, and the flow field is symmetric with respect to the radial, azimuthal and axial directions.…”

Simulations of the Rotor-Stator-Cavity Flow in Liquid-Floating Rotor Micro Gyroscope

“…Schouvelier et al [11,12] studied the correlation between Re and the gap-to-diameter ratio and the RSC flow field stability by photographing the wave structure and vortex structure in the flow field and mapped the flow fluctuations of disks in enclosed cavities. Watanabe et al [13,14] carried out simulations and experiments to study the effects of radial slits and the size of such slits on the fluid structure in cavities. Serre et al [15], through 3D direct numerical simulation, analyzed the relationship between the spatial structure and time of flows in annular and cylindrical cavities at different curvature and aspect ratios.…”

“…Heating and increased power consumption caused by solid-liquid frictional resistance [20,21] are especially significant in liquid-floating micro gyroscopes. However, the changes of fluid flow, temperature distribution, torque and driving power between disks at micro scale have not been fully studied [11][12][13][14]22]. Therefore, it is necessary to investigate the flows of microscale rotational disks.…”