| Summary: | 碩士 === 大葉大學 === 機械工程學系碩士班 === 91 === Motion of miscible magnetic fluid in a vertical capillary tube under a moving ring shape magnet are studied numerically. The magnet is adjusted dynamically to keep a constant distance from the mix tip on the centerline. Control parameters, such as magnetic pulling force, effective viscosity variation due to magnetization and the position of magnet, are analyzed systematically. Mass transfer performance is evaluated by several quantitative measurements. In general, stronger magnetic effect leads to better performance except the global amount of transferred mass that varies insignificantly. An asymptotic tip velocity is reached if magnetic strength beyond certain value. The influences of less effective viscosity lead to higher finger velocity, but shorter transferable distance. Unlike to the monotonic influences of magnetic pulling force and effective viscosity variation, there exists a potential optimal magnet position for the best effective mass transfer. Motion of miscible magnetic layer in a horizontal capillary tube under a moving ring-shaped magnet with an additional injecting flow from the right are studied numerically. The magnet is adjusted dynamically to maintain a constant distance from the front mixing interface on the centerline. Control parameters, such as magnetic strength, effective viscosity variation due to magnetization, diffusion and the position of the magnet, are analyzed systematically. Motion of the magnetic layer is evaluated by two quantitative measurements, i.e. movement of center of gravity and spread of layer width. In general, the moving speed of the center of gravity depends only slightly on the magnetic strength, and is found slower at a higher viscosity ratio and a closer placement to the front interface as well if the magnet is placed amid the layer. A weaker spread occurs in situations of stronger magnetic strength, lower viscosity parameters and also placements near the rear interface. A multi-front finger results if the magnet is positioned ahead of the front interface.
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