  We have simulated the motion of a single vertical, two-dimensional liquid
bridge spanning the gap between two flat, horizontal solid substrates of given
wettabilities, using a multicomponent pseudopotential lattice Boltzmann method.
For this simple geometry, the Young-Laplace equation can be solved
(quasi-)analytically to yield the equilibrium bridge shape under gravity, which
provides a check on the validity of the numerical method. In steady-state
conditions, we calculate the drag force exerted by the moving bridge on the
confining substrates as a function of its velocity, for different contact
angles and Bond numbers. We also study how the bridge deforms as it moves, as
parametrized by the changes in the advancing and receding contact angles at the
substrates relative to their equilibrium values. Finally, starting from a
bridge within the range of contact angles and Bond numbers in which it can
exist at equilibrium, we investigate how fast it must move in order to break
up.
