We investigate the formation of clusters of galaxies in an expanding u
niverse using a new code that regrids at a region of high density. In
particular, we investigate two models for the initial conditions, both
with the standard cold dark matter (CDM) power spectrum - one has Ohm
= 1, the other Ohm = 0.2. Both universes have H-0 = 100 km s(-1) Mpc(
-1) and Lambda = 0. The level of substructure in the final cluster can
be used as a discriminant of the cosmic density. We discuss various s
tatistics that can be measured observationally from clusters of galaxi
es, which can be used to discriminate between the two models. We find
that most of the statistics that use the clusters' member galaxies may
not be the best measures of substructure. Statistics that rely more o
n X-ray maps and other observables depending more directly on the mass
distribution could be better discriminants of Ohm.