  We report on results of recent, high resolution hydrodynamic simulations of
the formation and evolution of X-ray clusters of galaxies carried out within a
cosmological framework. We employ the highly accurate piecewise parabolic
method (PPM) on fixed and adaptive meshes which allow us to resolve the flow
field in the intracluster gas. The excellent shock capturing and low numerical
viscosity of PPM represent a substantial advance over previous studies using
SPH. We find that in flat, hierarchical cosmological models, the ICM is in a
turbulent state long after turbulence generated by the last major merger should
have decayed away. Turbulent velocites are found to vary slowly with cluster
radius, being $\sim 25%$ of $\sigma_{vir}$ in the core, increasing to $\sim
60%$ at the virial radius. We argue that more frequent minor mergers maintain
the high level of turbulence found in the core where dynamical times are short.
Turbulent pressure support is thus significant throughout the cluster, and
results in a somewhat cooler cluster ($T/T_{vir} \sim .8$) for its mass. Some
implications of cluster turbulence are discussed.
