  During coalescence of liquid drops contacting a solid, the liquid sweeps
wetted and solid-projected areas. The extent of sweeping dictates the
performance of devices such as self-cleaning surfaces, anti-frost coatings,
water harvesters, and dropwise condensers. For these applications, weakly- and
non-wetting solid substrates are preferred as they enhance drop dynamical
behavior. Accordingly, our coalescence studies here are restricted to drops
with contact angle 90{\deg} $\le \theta_{0} \le$ 180{\deg}. Binary sessile drop
coalescence is the focus, with volume of fluid simulations employed as the
primary tool. The simulations, which incorporate a Kistler dynamic contact
angle model, are first validated against three different experimental substrate
systems and then used to study the influence of solid wettability on sweeping
by modifying $\theta_{0}$. With increasing $\theta_{0}$ up to 150{\deg}, wetted
and projected swept areas both increase as drop center of mass heightens. For
$\theta_{0} \ge$ 150{\deg}, coalescence-induced drop jumping occurs owing to
the decreasing wettability of the substrate and a focusing of liquid momentum
due to the symmetry-breaking solid. In this regime, projected swept area
continues to increase with $\theta_0$ while wetted swept area reaches a maximum
and then decreases. The sweeping results are interpreted using the mechanical
energy balance from hydrodynamic theory and also compared to free drop
coalescence.
