Hydrodynamical simulations of a cloud of interacting gas fragments

We present a full hydrodynamical investigation of a system of self-contained, interacting gas 'cloudlets'. Calculations are performed using smoothed particle hydrodynamics, and cloudlets are allowed to collide, dissipate kinetic energy, merge and undergo local gravitational collapse. The numerical feasibility of such a technique is explored, and the resolution requirements examined. We examine the effect of the collision time and the velocity field on the time-scale for evolution of the system, and we show that almost all star formation will be confined to dense regions much smaller than the entire cloud. We also investigate the possibility, discussed by various authors, that such a system could lead to a power-law initial mass function by a process of repeated cloudlet coagulation, finding that in fact the inter-cloudlet collisions occur at too high a Mach number for merging to play an important part.