Abstract
Disintegration process of aqueous surfactant solutions injected from a fan spray nozzle has been clarified. Adsorption of surfactant molecules on the liquid surface causes time-dependent surface tension referred to as "dynamic surface tension". Therefore, when a new liquid surface is formed, surface tension decreases from the value of solvent to equilibrium value with time. This relaxation time of surface tension can be critical for the disintegration process of a liquid sheet that breaks up in comparable timescale. In this study, poly(oxyethylene)(10)octylphenyl ether was used as the surfactant, and the dynamic surface tension of the surfactant solution depending on concentration was measured by oscillating jet method. The break-up length of the liquid sheet and the amplitude of flapping waves inducing the disintegration were also measured by photography and laser induced fluorescence (LIF) method, respectively. The addition of the surfactant decreased the relaxation time of surface tension, and promoted the growth of the wave. However, break-up length increases with surfactant concentration. This discrepancy may be due to surface-stabilizing effect by the surfactant molecules, which is usually seen in a soap film.
