Chemical Engineering Science, Vol.61, No.4, 1074-1091, 2006
The effect of surfactant on the flow of a thin liquid film over a spinning disc
We examine the flow of a thin liquid film over a spinning disc in the presence of dilute insoluble surfactant. We use the integral method to derive a coupled system of equations that govern the axisymmetric evolution of the film thickness, radial flow rate, angular momentum and surfactant surface concentration; a linear equation of state is used for closure. This system of equations is parameterized by a modified Weber number, a Marangoni parameter, M, and a surface Peclet number, Pe(s). Numerical solutions of these equations reveal that the presence of surfactant gives rise to Marangoni stresses which interfere with the mechanisms of wave growth. For M similar to 0. 1, our results indicate that the formation of interfacial waves is suppressed. (c) 2005 Elsevier Ltd. All rights reserved.