界面活性剤水溶液における２次元自由液膜噴流の不安定特性

抄録

Growth characteristics of instability waves of a planer liquid sheet formed with surfactant solution have been clarified. It has been widely reported that a liquid sheet jet oscillates in sinuous shape because of Kelvin-Helmholtz instability and the growth rate of the instability wave depends on surface tension. Therefore, if the liquid is surfactant solution, the growth characteristics can depend on time-dependent surface tension referred to as dynamic surface tension, which originates from time delay required for adsorption of surfactant molecules to newly formed surface. In this study, the wave growth affected by the dynamic surface tension has been investigated as follows. At first, the relationship between the growth rate of the wave and time-invariant surface tension was determined using ethanol aqueous solutions with different concentrations. Secondly, the dynamic surface tension of the surfactant solution was measured, and surface tension varying with the distance from the nozzle was estimated. Thirdly, spatially varying amplitude of the wave was calculated from the results of above two steps. Finally, the calculated wave amplitude was compared with measured amplitude of the surfactant solution. The good agreement between calculated amplitude and experimental one proved that growth characteristic for surfactant solution depends on dynamic surface tension.