Investigation of the flow between obstructed corotating disks in enclosures

A experimental model of a computer hard disk drive was modified and measurements of the air flow in the obstructed space between a pair of disks were made. Four disks were centrally clamped to a hub which could be made to spin up to 4000 rpm in a transparent cylindrical enclosure. Two obstructions of rectangular cross-section and different lengths were alternately inserted along the midplane between the center pair of disks.; Radial profiles of the mean and rms circumferential velocity reveal that the region immediately downstream of both obstructions is one of low velocity and high rms. The presence of an inter-disk obstruction increases the intensity of the cross-stream motion. This accelerates the reestablishment of unobstructed flow characteristics downstream of the obstruction. The rms velocity values even further downstream of the long obstruction are smaller than those of the unobstructed flow, while the values for the short obstruction are approximately equal to the rms values in the unobstructed flow. The spectra obtained from the hotwire velocity records show evidence of eddy shedding from the long obstruction but not from the short obstruction.; The CUTEFLOWS code was first modified to numerically-model the unsteady three-dimensional obstructed disk flow in the laminar regime at 300 rpm. The mean flow velocity profiles are in qualitative agreement with those of the experiment. The computed flow was unsteady and strongly vortical downstream of both obstructions.; CUTEFLOWS was then modified to include an existing low Reynolds number k-l model. The obstructed flow was computed and compared with the experimental measurements at 1200 rpm. The profiles of the mean and rms of the circumferential velocity component were in very good agreement with the measurements, especially for the long obstruction. The rms was subdivided into its turbulent fluctuation component and its mean flow oscillation component. This revealed that 20 degrees downstream of the long obstruction the majority of the rms at large radii was due to turbulent fluctuations while the majority of the rms at small radii was due to mean flow oscillations. The spectra of both obstructed flows showed dominant peaks with values of frequency in good agreement with the measurements. (Abstract shortened by UMI.)...