| Summary: | 碩士 === 國立宜蘭大學 === 機械與機電工程學系碩士班 === 101 === The surface tension of the magnetic fluid （FHD） is a very important parameter for the study of magnetic flow force. Experimental surface tension estimates by the interaction of the magnetization and the magnetic field strength of the test sample through the amendment of the Langevin permeability function derived from the apparent weight change. In this study, further found that static equilibrium of apparent weight change closely depends on magnetic field density, magnetic susceptibility of the magnetic fluid and magnetic particle volumetric concentration. In order to evaluate ferro-surface tension corresponding to magnetic flux as well as relevant working parameters, a simple set of pull-ring experimental device is then set up and used to estimate the magnetic fluid surface tension coefficient, which features as an economical and efficient utility. Under the working magnetic field strength falls within 0 ~ 40mT, Experimental results on surface tension coefficient made from commercial sample provided by Matsumoto （VSM method） shows good agreement with that accessed from present method proposed. The Rayleigh-Taylor model is an important theory dealing with ferro-hydrodynamic （FHD） instability, which will be utilized to predict the ferro-surface tension of ferrofluid in this study. Before the critical ferro-magnetization has been induced, an approximation result generalized from proposed model could be developed under the testing system remains static in normal field, i.e., a simple proportional relation existing between ferro-surface tension and the increasing rate of apparent ferro-weight, attributed to magnetic attraction, might be carried out. That will make the predicted ferro-surface tension become easier. Then the the Rayleigh theoretical formula calculation comparison, the experimental method can be fairly consistent confirmed.
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