  Direct simulations of phase-change and phase-ordering phenomena are becoming
more common. Recently qualitative simulations of boiling phenomena have been
undertaken by a large number of research groups. One seldom discussed
limitations is that large values of gravitational forcing are required to
simulate the detachment and rising of bubbles formed at a bottom surface. The
forces are typically so large that neglecting the effects of varying pressure
in the system becomes questionable. In this paper we examine the effect of
large pressure variations induced by gravity using pseudopotential lattice
Boltzmann simulations. These pressure variations lead to height dependent
conditions for phase co-existence and nucleation of either gas or liquid
domains. Because these effects have not previously been studied in the context
of these simulation methods we focus here on the phase-stability in a one
dimensional system, rather than the additional complexity of bubble or droplet
dynamics. Even in this simple case we find that the different forms of
gravitational forces employed in the literature lead to qualitatively different
phenomena, leading to the conclusion that the effects of gravity induced
pressure variations on phase-change phenomena should be very carefully
considered when trying to advance boiling and cavitation as well as
liquefaction simulations to become quantitative tools.
