  Three-dimensional simulations with fully resolved hydrodynamics are performed
to study the dynamics of a single squirmer under gravity, in order to clarify
its motion in the vicinity of a flat plate. Different dynamics emerge for
different gravity strengths. In a moderate gravity regime, neutral squirmers
and pullers eventually stop moving and reorient in a direction perpendicular to
the plate; pushers, instead, exhibit continuous motion in a tilted direction.
In the strong gravity regime, all types of squirmers sediment and reorient
perpendicularly to the plate. In this study, the chirality is introduced to
model realistic micro-swimmers, and its crucial effects on the swimmer dynamics
are presented.
