DEVELOPMENT OF THE SYSTEM FOR MEASURING THREE DIMENSIONAL UNSTABLE FLOW IN MAGNETIC STORAGE DISKS

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The unstable flow between two rotating disks has recently considered as an important research theme in connection with disk-flutter, disk-crash; thermal problems and the behavior of dusts. Only a few reports can be found on this topic because the flow is so complicated and has three dimensional structures.In this study, we developed a system for measuring three dimensional velocity fields and the frequency of the unstable flow by using hydrogen bubble method and image enhancement technique. We performed the project according to the following procedure; (1)Design and manufacturing of the experimental apparatus, (2)Design and manufacturing of the control system for driving disks, (3)Design and manufacturing of electric circuits for generating hydrogen bubbles, (4)Experiment, (5)Development of the method for image analysis, (6)Development of the software for image analysis, (7)Development of the verification method for the system developed in this study.The experimental apparatus is compo … More sed of the acrylic cylinder simulating the shroud and two parallel rotating glass disks. In the middle of two disks, we installed a slender stainless wire for generating hydrogen bubble. The electricity for the wire is supplied through a slipring. By using two CCD cameras, one is for top view and another is for side view, the device for composing the image from two CCD cameras and a video tape recorder,we could record the behavior of three dimensional bubble motions. After that by using the apparatus for image enhancement, we could trace the instantaneous three dimensional motion of bubbles.Finally, to check the effectiveness of this system, we simulated the motion of a single bubble generated just in the middle of two rotating disks. As a result, we recognized that this system is effective for observing the unstable flow from the rotating coordinate system quantitatively, but is not effective for observing the flow in the direction of the axis of rotation because of the buoyant force acting on the bubble. Less