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

当两个平行的圆盘在同一轴上旋转时，圆盘之间的流体流动变得不稳定，并产生非轴对称流型，这些流型与轴的旋转方向相同，如旋转失速。在计算机系统中，作为外部存储单元的磁盘设备也会产生同样的不稳定流动现象，有时会给设备带来故障，如磁盘颤动、访问失误或浮动磁头崩溃。该系统由以下三个子系统组成：(1)转盘系统两个平行的圆盘在水中旋转。为了显示非定常流动，在其中一个圆盘上安装了一根不锈钢丝作为阴极，从其中一个圆盘上周期性地产生微小的氢蒸气。(2)测量系统摄像机与圆盘系统同步旋转，捕捉氢气的行为，并记录在录像带上。(3)视频数据分析系统从录像带中再现一个时期内任何时刻的非定常流动的图像。它们被自动数字化，并获得氢气的轨迹，由此确定非定常流动的速度矢量。(A)圆盘之间的流动由定常分量和非定常分量组成。当圆盘的速度越高，圆盘之间的距离越大，后者的幅度就越大。(B)稳定分量的速度分布与半径不成正比，类似于固体旋转。

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.