We model molecular outflows produced by the time dependent interaction between a stellar wind and a rotating cloud envelope in gravitational collapse , studied by Ulrich .
We consider spherical and anisotropic stellar winds .
We assume that the bipolar outflow is a thin shocked shell , with axial symmetry around the cloud rotation axis and obtain the mass and momentum fluxes into the shell .
We solve numerically a set of partial differential equations in space and time , and obtain the shape of the shell , the mass surface density , the velocity field , and the angular momentum of the material in the shell .
We find that there is a critical value of the ratio between the wind and the accretion flow momentum rates \beta that allows the shell to expand .
As expected , the elongation of the shells increase with the stellar wind anisotropy .
In our models , the rotation velocity of the shell is the order to 0.1 - 0.2 km s ^ { -1 } , a factor of 5-10 lower than the values measured in several sources .
We compare our models with those of Wilkin and Stahler for early evolutionary times and find that our shells have the same sizes at the pole , although we use different boundary conditions at the equator .