Development of an Automatic Analyzer System of Unsteady Flows Generated in Magnetic Disc Equipment

当两个平行圆盘在同一轴上旋转时，圆盘间的流体流动变得不稳定，产生非轴对称流型，这种流型与轴同向旋转，类似旋转失速。在计算机系统中作为外部存储器的磁盘设备中也会产生同样的不稳定流动现象，有时会引起磁盘颤动、存取错误或浮动磁头破裂等故障，本研究开发了一种自动分析系统，以获得两个平行旋转磁盘间的不稳定流动信息。该系统由以下三个子系统组成。(1)旋转圆盘系统两个平行的圆盘在水中旋转。为了使不稳定流动可视化，在其中一个圆盘上安装了一根不锈钢丝作为阴极，从阴极定期产生少量的氢蒸汽。(2)测量系统摄像机与磁盘系统同步旋转，捕捉氢蒸汽的行为，并记录在录像带上。(3)视频数据分析系统从录像带中再现了一个周期内任意时刻的非定常流图像。对这些数据进行了自动数字化处理，得到了氢蒸汽的运动轨迹，并由此确定了非定常流的速度矢量。(a)圆盘间的流动由定常流动和非定常流动组成。当盘的速度越高，盘之间的距离越大时，后者的幅度越大。(b)稳定分量的速度分布与半径不成比例，就像固体旋转一样。

When two parallel discs are rotating on the same shaft, the fluid flow between the discs becomes unstable and non-axisymmetric flow patterns are generated, which rotate in the same direction as the shaft like rotating stall. The same unstable flow phenomena are generated in the magnetic disc equipment used as the external memory unit in the computer system, and sometimes cause troubles to the equipment, such as disc flutter, access miss, or floating head crach.In this research an automatic analyzer system is developed to get informations about the unsteady flows between the two parallel, rorating discs. The system consists of the following three subsystems.(1) Rotating Disc System The two parallel discs rotate in water. To visualize the unsteady flows, a stainless wire is mounted on one of the discs as cathode, from which small hydrogen vapors are generated periodically.(2) Measuring System A video camera rotates synchronously with the disk system and catches the behaviors of the hydrogen vapors, which are recorded on video tape.(3) Video Data Analyzing System Pictures at any instants of time over one period of the unsteady flows are reproduced from the video tape. They are digitized automatically and the trajectories of the hydrogen vapors are obtained, from which velocity vectors of the unsteady flows are determined.From this research, the following results are obtained. (a) The flow between the discs consists of the steady component and the unsteady one. The amplitudes of the latter is larger, when the speed of the disc is higher and the distance between the discs is larger.(b) The velocity distribution of the steady component is not proportional to the radius, like a solid rotation.