  In bulk ferroelectric liquid crystals, the molecular director twists in a
helix. In narrow cells, this helix can be unwound by an applied electric field
or by boundary effects. To describe helix unwinding as a function of both
electric field and boundary effects, we develop a mesoscale simulation model
based on a continuum free energy discretized on a two-dimensional lattice. In
these simulations, we determine both the director profile across the cell and
the net electrostatic polarization. By varying the cell size, we show how
boundary effects shift the critical field for helix unwinding and lower the
saturation polarization. Our results are consistent with experimental data.
