EFFECT OF INTERFACIAL MOBILITY ON THIN-FILM DRAINAGE

Analytical equations for the radial drainage of uniform thin viscous f ilms are obtained in terms of the variation in surface velocities and velocity gradients with position and time. These allow the effect of c irculation in the adjacent phases and radial surface or interfacial te nsion gradients to be allowed for. The resultant coalescence time t(c) may be estimated from the equation t(c) = 3pimun2r(f)4/16fh(c)2, wher e n is given by 4/n2 = 1 + (3mur(d)/mu(d)h(i)[1 + (pir(f)3/2fh(i))(par tial derivative sigma/partial derivative r)n] for a drop of radius rd approaching its homophase. Good agreement with available experimental values is obtained for drops resting at a stationary interface or movi ng along an inclined film. (C) 1994 Academic Press, Inc.