  The mixed morphology class of supernova remnants has centrally peaked X-ray
emission along with a shell-like morphology in radio emission. White & Long
proposed that these remnants are evolving in a cloudy medium wherein the clouds
are evaporated via thermal conduction once being overrun by the expanding
shock. Their analytical model made detailed predictions regarding temperature,
density and emission profiles as well as shock evolution. We present numerical
hydrodynamical models in 2D and 3D including thermal conduction, testing the
White & Long model and presenting results for the evolution and emission from
remnants evolving in a cloudy medium. We find that, while certain general
results of the White & Long model hold, such as the way the remnants expand and
the flattening of the X-ray surface brightness distribution, in detail there
are substantial differences. In particular we find that the X-ray luminosity is
dominated by emission from shocked cloud gas early on, leading to a bright peak
which then declines and flattens as evaporation becomes more important. In
addition, the effects of thermal conduction on the intercloud gas, which is not
included in the White & Long model, are important and lead to further
flattening of the X-ray brightness profile as well as lower X-ray emission
temperatures.
