MODELS OF MOLECULAR OUTFLOWS

In this contribution, I present a broad ''historical'' review of the v arious hydrodynamical models that have been considered for explaining molecular outflows, and of their merits and failures when compared wit h observations. Wind-driven bubbles, viscous jet mixing-layers, and je t bowshocks, are discussed in turn. Most general properties of outflow s can be understood in terms of a simple bowshock model. However, the detailed structure of outflows is more complex and not yet fully under stood, given the presence of time variability in the jet velocity and/ or direction. Finally, I discuss constraints on wind properties (momen tum, mass-loss rate, radius) that can be derived from molecular outflo ws driven by jet bowshocks.