非軸対称容器内の回転円盤に駆動される平面速度場から再構築した三次元流れ構造の検討

抄録

Rotational flows driven by stacked disks in an enclosure as seen in fluid machinery and hard disk drive (HDD) exhibit complex three-dimensional behavior. In experiments, the flow velocities are accessible in the planes parallel to the disk surface, but direct evaluation of the ones perpendicular to the disk surface remains difficult. In this study, we attempted to reconstruct the axial velocities based on the integration of the mass conservation using the in-plane velocity fields acquired at multiple planes parallel to the disk surfaces. For the velocity measurements, we applied two-dimensional, two-component particle image velocimetry (PIV). The averaged axial velocities were reconstructed through the numerical integration of the axial velocity gradients, which were obtained through the numerical differentiations of the in-plane velocity gradients of the averaged velocity fields of the PIV data. The method was applied to a rotating flow driven by the stacked disks mounted in a non-axisymmetric enclosure equipped with arm assembly. The flow was a 2.25 times scaled model of hard disk drive (HDD) for information storage. The model allows an optical access for flow visualization and PIV measurement with the refractive index of the working fluid matched to that of the resin of the transparent HDD model. The PIV measurements were performed at 21 planes in the flow at the Reynolds number of 7.4 × 10⁴ corresponding to 5400 rpm in a 3.5-inch HDD. Based on the proposed scheme, the averaged axial velocities were reconstructed based on the method. They were examined at different circumferential angles. The reconstructed velocity fields revealed the existence of secondary flow structure in the region downstream of the arm. The reconstruction of the axial velocity provides a method to investigate the complex three-dimensional structure of the flow.