移動接触線近傍の流れ場に及ぼす液体・固体物性の影響(流体工学,流体機械)

概要

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The flow field near a moving contact line was measured with the particle imaging velocimetry technique. The test liquids of pure water, ethylene glycol (EG), dimenthyl sulfoxide (DMSO) and polydimethylsiloxane (PDMS) of which surface tensions range from 19mN/m to 72mN/m were used with the solid materials of glass, polymethylmethacrylate (PMMA) and polytetrafluoroethylene (PTFE). The combination of these materials varied the contact angle from zero to 90 degrees. Each solid material was withdrawn from each liquid into Ar gas atmosphere at a constant speed of 0.62mm/s. The observed flow fields were qualitatively different from the theoretical ones obtained with a linear model when the test liquid was either of water, EG or DMSO with the contact angle less than 90°. It is found that, for such flow fields, the viscous tangential stress on the gas-liquid interface estimated for the liquid phase is much larger than that for the gas phase. The stress in the liquid phase forces the liquid on the interface to flow toward the contact line. The Marangoni stress induced by inhomogeneous distribution of slight amount of impurity (surfactant) on the gas-liquid interface is the most presumable mechanism which compensates for the difference between the viscous stresses for the both phases on the interface.
2010-09-25