Fig. 4: Extensional and swept areas during coalescence showing the evolution of the x-axis x_p(t) and y-axis y_p(t) projected extensions.

The contact-line position (dashed blue line) is superimposed on the top view. Instantaneous cumulative projected swept areas \({{{\mathscr{P}}}}(t)\) are indicated by the black silhouettes, with the final cumulative projected swept area \({{{{\mathscr{P}}}}}_{\infty }\) shown on the rightmost image. The circles on \({{{{\mathscr{P}}}}}_{\infty }\) (red solid) represent the initial projected drop areas.