Oscillatory driven cavity with an air/water interface and an insoluble monolayer: Surface viscosity effects

Flow in a planar cavity bounded by stationary side walls, a flat gas/liquid interface covered by an insoluble monolayer, and driven by sinusoidal moti on of the floor is examined numerically. Navier-Stokes computations with th e Boussinesq-Scriven surface model are presented utilizing the equation-of- state measured for a vitamin KI monolayer on the air/water interface. The r esults identify a range of initial surfactant concentration for which the s urface velocity is sensitive to the surface viscosity B (sum of surface she ar and dilatational viscosities) down to 10(-2) surface Poise. Thus, the st udy suggests a practical method for determining surface viscosities consist ing of the measurement of the motion of a tracer particle on the interface and comparisons with numerical computations at various values of B. (C) 200 1 Academic Press.