A disjoining pressure valid for nonzero contact angles

COLL 418

Harris Wong and Qingfang Wu. Mechanical Engineering Department, Louisiana State University, Baton Rouge, LA 70803
A thin fluid film is subject to intermolecular forces, which are commonly expressed by the disjoining pressure P=P(h), where h is the film thickness. This disjoining pressure becomes unbounded as h tends to zero, and therefore cannot allow a fluid film to end at a solid surface. We derive rigorously a new expression for the disjoining pressure and obtain P=P(h, hx, hxx), where x is a coordinate along the solid surface. The new expression allows non-zero contact angles. It simplifies to the original form P=P(h) when the slope of the film is zero. We solve several problems using the new expression. We will describe the derivation and the applications in this talk.