Oscillatory Driven Cavity with an Air/ Water Interface and an InsolubleMonolayer: 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 motion of the floor is examined numerically. Navier– Stokes computations with the Boussinesq–Scriven surface model are presented utilizing the equation-of-state measured for a vitamin K1 monolayer on the air/water interface. The results identify a range of initial surfactant concentration for which the surface velocity is sensitive to the surface viscosity B (sum of surface shear and dilatational viscosities) down to 10−2 surface Poise. Thus, the study suggests a practical method for determining surface viscosities consisting of the measurement of the motion of a tracer particle on the interface and comparisons with numerical computations at various values of B. C © 2001 Academic Press