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

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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.