Jet flows are important in many astrophysical objects, from protostars
and Galactic superluminals within our own Galaxy to extragalactic radio
sources. Since the evolution of these flows follow from nonlinear
dynamical systems of equations (e.g., hydrodynamics or magnetohydrodynamics),
numerical simulations are needed to more fully understand the nature of
these flows. I will focus on the effects that magnetic fields will have
on the amount of mass entrained by the flow. I will also compare the mass
entrainment rate with simulated intensity (at radio wavelengths) images
of the simulated jets, so that observable structures may be compared with
the underlying flow. Linear stability analysis suggests an explanation
for the initial spatial growth of mass entrainment in supermagnetosonic
flows.