Dynamics of inertia dominated binary drop collisions

A head-on impact of two equal drops is studied theoretically. The initial drops deformation, the radial expansion of the obtained liquid mass, and the subsequent axial stretching are considered. The deformation of the drop in the radial direction is governed by the motion of a rim bounding an expanding lamella, whereas the axial deformation of the drop is governed by the motion of two globules formed at the ends of a stretching liquid jet. The equations of motion of the rim and of the globules are obtained from the mass and the momentum balance. The theory accounts for the inertial effects, surface tension and the viscous stresses. The theoretical predictions of the drop diameter and its length are compared with experiments. The agreement is rather good in spite of the fact that no adjustable parameters are used. (C) 2004 American Institute of Physics.