鉛直加振を受けるメニスカスの周期変形により励起される円筒容器内界面波の特性(流体工学,流体機械)

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Standing waves excited by the periodic deformation of meniscus are investigated for the interface between two immiscible fluids confined in a vertical cylindrical container. When meniscus is subject to vertical oscillation, it can be deformed due to the time-dependent change of the capillary length, which is the horizontal scale of the meniscus, and the periodic deformation excites interface waves. The resonance characteristics of the excited wave is experimentally and numerically investigated under pinned-edge contact line condition and it is found that the resonant wave height grows with increase in the absolute deviation of the static contact angle from 90 degrees. A linear analysis model is derived under the assumption of quasi-static deformation of the meniscus with respect to the change in the vertical acceleration. The model shows that the magnitude of the excitation term is in proportion to tan|π/2-θ_0| with θ_0 the static contact angle, and to the fourth power of the exciting frequency. With appropriate decay factor, the linear model well reproduces the resonance curve of the wave height and the dependence of the resonant wave height on the static contact angle observed in the experiments and the numerical simulations.
2009-06-25