We seek to study the dynamics of mixing and transport processes in the presolar cloud and in the solar nebula, in the context of isotopic heterogeneity introduced either by shock-triggered collapse of the presolar cloud or by infall from an x-wind outflow, the two leading explanations for the widespread evidence of short-lived radioactivities in chondritic refractory inclusions and, much more rarely, in chondrules. We have developed a new hydrodynamical code for studying these problems, using the FLASH adaptive mesh refinement code. FLASH allows the problem of shock-wave triggering and injection to be studied with an unprecedented degree of high spatial resolution, which is likely to be critical to the question of simultaneous triggering and injection when nonisothermal shock front thermodynamics is employed. The FLASH code will permit extending these investigations down to the scale of the solar nebula, where nebular transport and mixing processes can be studied in general terms, applicable to isotopically heterogeneous grains falling onto the nebular surface as a result of either shock-triggered collapse or x-wind outflows. We will seek in part to learn whether spatial and temporal heterogeneity inherited from such sources can survive subsequent nebular mixing processes and can help to explain certain isotopic abundance patterns seen in the inner Solar System and the asteroid belt. The development of the FLASH code should also prove useful for Boss's studies of the formation of giant planets by the disk instability mechanism.
