Visualization of Coalescence of Two Liquid Drops over a Superhydrophobic Surface

Coalescence phenomenon of liquid drops of equal and unequal volumes over a hydrophobic surface is reviewed and presented using images from experiments and numerical simulations. Bond number based on the combined volume is in the range of 0.01-0.2. As the drops coalesce, a great variety of interface shapes appear as the merged drop approaches equilibrium. These interface shapes are visualized using a high-speed camera and followed by an examination of the timescales, axisymmetry, bridge formation, dynamic contact angle variation, energy budget, and shear rate.