On the flow in the unobstructed space between shrouded corotating disks

Abstract

A model of a computer hard disk drive was constructed and measurements of the air flow in the unobstructed space between a pair of disks were obtained. The disks were centrally clamped to a common hub, and rotated within an axisymmetric (cylindrical) enclosure or shroud. Measurements of the circumferential velocity component were made at four radial locations and along the midplane at three rotation rates (0 = 300, 1200, and 3600 rpm) using a laser-Doppler velocimeter. The resulting mean and rms circumferential velocity profiles are presented and discussed. The data show that the circumferential velocity component profiles are fairly uniform in the axial direction in the space between the disks, except near the shroud where the flow is strongly sheared. The circumferential velocity peaks at a critical radius. Between the hub and the critical radius location the flow is in solid body rotation. Between the critical radius and the shroud the circumferential velocity decreases to zero, gradually at first and then very quickly as the shroud is approached. Analysis based on simplified force balance considerations facilitates the interpretation of the experimental observations and leads to improved understanding of the complex flow phenomena. Numerical calculations of the present configuration assuming axisymmetric steady flow were performed by Chang et al.(submitted to Int. J. Heat Mass Transfer). These calculations show reasonable agreement with the averaged velocity data but, for the reasons discussed, fail to reproduce features of the rms distribution associated with non turbulent flow unsteadiness.

Circulation in a Short Cylindrical Couette System

“…In that case, rigid-body rotation would be expected to appear in the inner part of the flow. Actually, such a fluid-dynamical system has been investigated in the literature in connection with hard disk drives for computers [19][20][21][22][23].…”

A Study on the Efficacy of Flow Mitigation Devices in Hard Disk Drives

“…9). The inner and outer edges of the rib are a source of vorticity shedding too, which increases the turbulence intensity of the downstream flow (see (8) in Fig. 10).…”

Phase‐Averaged Method Applied to Periodic Flow Between Shrouded Co‐ Rotating Disks

“…These consist of an inner region (r * < 0.55) where the fluid velocity is within 10% of the disk velocity and an outer region (r * > 0.55) where the normalized 414 S. H. WU AND Y. M. CHEN velocity decreased linearly to ∼ =63% of the disk velocity at the disk edge (r * = 1). By illuminating the micro-sized mineral oil droplets with a laser sheet, Humphrey and Gor (1993) visualized the crossstream flow in an experimental apparatus similar to that used by Schuler et al (1990). Humphrey, Schuler, and Weber (1995) numerically investigated the unsteady streamlined motion of a constant property fluid in the unobstructed space between disks co-rotating in a fixed cylindrical enclosure using a time-explicit algorithm.…”

“…Abrahamson et al (1988Abrahamson et al ( , 1989Abrahamson et al ( , 1991 employed bromothymol blue dye and a hydrogen bubble technique for flow visualization and reported the existence of a center core region in solid body rotation and the presence of circumferentially periodic flow structures with a strong component of axial vorticity near the shroud, processing at roughly 75% of the disk rotation rate. Schuler et al (1990) also employed a LDV to measure the mean and rms of the circumferential velocity component between the central pair of four co-rotating disk flow. As being normalized with the local disk surface velocity, the mean and rms velocity measured by Tzeng, Munce, and Crawforth (1991) at Re = 7.9 × 10 4 show fairly good agreement with the data measured by Schuler et al at Re = 8.9 × 10 4 .…”