ASYMPTOTIC ANALYSIS OF AXISYMMETRICAL DROP SPREADING

We study in this paper the time evolution of the spreading process of a small drop in contact with a flat dry surface, using asymptotic tech niques. We reduced the problem by solving a quasisteady self-similar m acroscopic problem and matched with the precursor region solution, whe re the van der Waals forces are important. A final nonlinear third-ord er ordinary differential equation has been solved numerically using sh ooting methods based on the fourth-order Runge-Kutta techniques. We ob tained how the capillary number changes when the drop size decreases w ith time. The evolution process then diverges slightly from that obtai ned using the spherical cap approximation. The influence of gravity is also considered for both hanging and sitting drops. [S1063-651X(98)09 409-4].