THE DRAINAGE AND RUPTURE OF PARTIALLY-MOBILE FILMS BETWEEN COLLIDING DROPS AT CONSTANT APPROACH VELOCITY

A numerical study is presented of the drainage and rupture of the liqu id film between two drops whose centres approach each other at constan t velocity. The considerations are restricted to the partially-mobile case (in which the drop viscosity is rate-determining) and to small ap proach velocities. The latter restriction permits a transformation of the governing equations to a single universal form, which is solved wi th the help of boundary integral theory. As in the constant force case , the numerical results show the formation of a dimple but the final d rainage behaviour differs considerably. Finally, the influence of van der Waals forces is investigated and the results are shown to correspo nd well with a simple model proposed earlier for the effective critica l film-rupture thickness.