01. Experimental/Computational Fluid Dynamics

Rotating flows driven by corotating disks in enclosure are encountered in fluid machinery, flywheel, and information storage device. The flow is known to exhibit complex three-dimensional structure due to the centrifugal force working in a confined environment. We experimentally investigate three-dimensional structure of rotating flow driven by corotating disks mounted in a non-axisymmetric enclosure with shrouded wall and arm insertion. The flow is a simplified model of 3.5” hard disk drive (HDD) for information storage. Experiment was performed using simplified HDD model made of transparent material. It consists of a pair of corotating disks with simplified arm assembly and shroud opening area. The refractive index of the working fluid was matched to the model material, so that the whole flow was transparently observed while the mechanical properties of the solid and fluid were maintained. As a similarity parameter, Reynolds number based on the disk radius was employed. The model was 2.25 times scaled and the operating condition was matched to the Reynolds number at 7.4x10^4 corresponding to 5400 rpm in a real 3.5” HDD. The investigation is based on the measurement of two-dimensional velocity fields with particle image velocimetry (PIV). The axial flow was reconstructed using planar velocity fields obtained with PIV measurement at multiple planes based on the mass conservation. As a demonstration, we developed a reconstruction scheme and applied it to the region with the arm assembly deeply inserted into the disk region. The reconstructed mean velocity data show three-dimensional structure of the flow around the inserted arm assembly. The flow around the arm has to either climb over or go under the arm due to the blockage. We report on the reconstructed three-dimensional flow around the arm assembly and the other regions. The reconstruction scheme will be described with the investigation of the reconstruction uncertainty.