  The dynamics of two vertically coalescing drops and a pool of the same liquid
have been investigated using a Coupled Level Set and Volume of Fluid (CLSVOF)
method. Such a configuration enables us to study the dynamic interaction of an
arbitrary-shaped liquid conglomerate, formed owing to drop-drop coalescence,
with a pool. Similar to drop-pool and drop-drop interactions, partial
coalescence is observed when a conglomerate interacts with a pool. The presence
of the pool below the father drop is found to influence the coalescence
characteristic of the two drops. At the same time, the movement of the
capillary waves resulting from the interaction of two drops governs the
coalescence dynamics of the conglomerate with the pool. As liquid interfaces
interact and generate capillary waves at multiple locations, complex
trajectories of capillary waves are observed, which play a crucial role in
determining the pinch-off characteristics of the satellite during
conglomerate-pool interaction. We examine the effect of the ratio of the
diameters of the lower/father drop to the upper/mother drop (D_r) on the
coalescence dynamics while maintaining the size of the mother drop constant.
The variation in the coalescence dynamics due to change in $D_r$ is quantified
in terms of the residence time (tau_r), pinch-off time (tau_p) and the
satellite diameter to conglomerate diameter ratio (Ds/Dc). The coalescence
dynamics of the conglomerate is then compared with that of an equivalent
spherical drop of the same volume and also with that of a drop initialized with
the same shape as that of the conglomerate. Finally, the regions of complete
and partial coalescence for the conglomerate-pool interactions are demarcated
on the Weber number - diameter ratio (We-Dr) space.
