Effect of turbulent viscosity on the isothermal collapse of a rotating protostellar cloud

The isothermal collapse of a uniform-density pure H2 10-K protostellar cloud of 1 solar mass rotating rigidly at 3.5 x 10 to the -13th/s is investigated analytically, modifying the two-dimensional Eulerian-hydrodynamics simulation of Black and Bodenheimer (1975 and 1976) to include turbulent-viscosity effects and imposing constant-volume boundary conditions. The results are presented graphically and compared with those for the corresponding inviscid cases and with the phenomenological model of turbulent viscosity of Regev and Shaviv (1980 and 1981). Viscosity is found to retard collapse and increase the density toward the center, but not to suppress the initial ring structure completely (for realistic values of the viscosity force) during the time the collapse could be followed in the simulations.