Journal of Colloid and Interface Science, Vol.181, No.1, 344-346, 1996
Surfactant-Induced Stationary Modes on a Cylindrical Fluid Jet
An obstacle in the path of a cylindrical fluid jet creates axisymmetric stationary capillary waves upstream of the obstacle, These waves can be easily observed on low velocity water jets issuing from taps. The presence of a surfactant on the jet surface will give rise to surfactant induced stationary modes, Ln this note we derive the dispersion relation for surface waves on a cylindrical fluid jet with an insoluble monolayer of surfactant on its surface, with a view to investigating surfactant induced stationary modes. The dispersion is seen to have infinite wavelength stationary solutions corresponding to an exponential decrease of excess surfactant concentration. The decay coefficient of these modes increases with increasing jet velocity and decreases with increasing surfactant concentration. This phenomenon offers a novel method for determining the interfacial properties of a freshly formed surface.