細管から射出される界面活性剤水溶液の液滴形成に対する動的表面張力の影響(<小特集>非ニュートン性,機能性を示す複雑流体の流動と応用)

概要

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Effects of dynamic surface tension on the droplet formation of surfactant solutions were studied. Test fluids used were aqueous solutions of CTAB at several surfactant mol concentrations (C_D) and CTAB/NaSal aqueous solutions at C_D=1.0mM and at three mol concentrations of NaSal. A droplet formed when a surfactant solution was injected from a capillary tube was investigated and the relation between the droplet diameter and the injection velocity V was measured. The size of droplet was evaluated by an equivalent droplet diameter Dexp, which is the diameter of sphere whose volume is same as that of a droplet injected. For the CTAB systems, Dexp increased with increasing V at relatively low velocities because the dynamic tension also increased. However, the diameter decreased with increasing the velocity at relatively high velocities. This phenomenon can be qualitatively predicted from an equation of the force balance at a capillary exit when the effect of surface tension is evaluated using the dynamic surface tension. For the CTAB/NaSal systems, Dexp increased with increasing V at relatively low velocities and reached a steady state value. This phenomenon was also predicted qualitatively with the force balance equation.
2009-05-25