Observed equilibrium drop shapes were compared with the
equilibrium raindrop shapes using Beard and Chuang's (1987) theoretical
analysis. Furthermore, drop fall velocities at a given fall distance
were compared using the predicted terminal velocities of Eq. (1) developed
by Atlas et al. (1973). The following subsections describe our
quantitative efforts to delineate these fall zones based upon the transient
shape (for the extent of Zone I), the equilibrium shape (for the
onset of Zone II), and the terminal velocity (for the onset of Zone III)
criteria.
3.1. Drop shape evolution
Generated drops were expected to exhibit multimode oscillations
that are governed by the axisymmetric, transverse, and horizontal oscillation
modes of the fundamental harmonic (see Fig. 1). To determine
the presence/absence of large-amplitude drop oscillations generated
by detachment fromthe source (hence, the extent of Zone I), the evolution
of the aforementioned shape parameters with fall distance was analyzed,
the results of which are presented in Figs. 8–11. Moreover,
Fig. 9.