Under the micro-gravity environment in space, it is possible to hold a liquid drop without using container. The electrostatic levitation is one of the containerless processing techniques. Using this technique, thermo-physical properties of extreme high temperature molten metals have been measured. For example, the surface tension and viscosity have been estimated from the resonance frequency and the damping constant respectively with an oscillating drop method. This method is based on theoretical equations derived under linear approximations. However, an actual levitating drop includes nonlinear effects. Nonlinear effects should be taken into account for highly precise measurements of physical properties, but it is unknown experimentally. The purpose of the present study is to investigate nonlinear effects of a levitating liquid drop from fluid-dynamic point of view. In the present study, at first, axisymmetric oscillation was applied to a liquid drop levitated by electrostatic force and the oscillation frequency was related to the oscillation amplitude. Next, the rotation in the horizontal direction was applied. The drop deformation and the dependence of resonance frequency on rotational angular velocity were investigated. These experimental results agreed with theoretical predictions.

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