  The abundance and internal characteristics of rich clusters of galaxies can
provide useful constraints on models of large--scale structure formation. This
article will review some recent three dimensional, multi--fluid simulations of
cluster dynamics and discuss their impact on issues raised from optical and
X-ray observations of clusters. In `bottom--up' formation scenarios (such as
the ubiquitous cold dark matter model), galaxies form before rich clusters;
hence, cluster formation is intimately linked to galaxy formation which, in
turn, is tied to star formation. I will examine two issues which appear
relatively insensitive to galaxy/star formation --- the baryon fraction in
clusters and the connection between X--ray morphology and $\Omega_o$ --- and
end with a topic that is intimately linked to it --- dynamical biases in the
cluster galaxy population.
