  We present numerical simulations of the adiabatic interaction of a shock with
a clumpy region containing many individual clouds. Our work incorporates a
sub-grid turbulence model which for the first time makes this investigation
feasible. We vary the Mach number of the shock, the density contrast of the
clouds, and the ratio of total cloud mass to inter-cloud mass within the clumpy
region. Cloud material becomes incorporated into the flow. This "mass-loading"
reduces the Mach number of the shock, and leads to the formation of a dense
shell. In cases in which the mass-loading is sufficient the flow slows enough
that the shock degenerates into a wave. The interaction evolves through up to
four stages: initially the shock decelerates; then its speed is nearly
constant; next the shock accelerates as it leaves the clumpy region; finally it
moves at a constant speed close to its initial speed. Turbulence is generated
in the post-shock flow as the shock sweeps through the clumpy region. Clouds
exposed to turbulence can be destroyed more rapidly than a similar cloud in an
"isolated" environment. The lifetime of a downstream cloud decreases with
increasing cloud-to-intercloud mass ratio. We briefly discuss the significance
of these results for starburst superwinds and galaxy evolution.
