During their evolution massive stars can reach the phase of critical rotationwhen a further increase in rotational speed is no longer possible. Directcentrifugal ejection from a critically or near-critically rotating surfaceforms a gaseous equatorial decretion disk. Anomalous viscosity provides theefficient mechanism for transporting the angular momentum outwards. The outerpart of the disk can extend up to a very large distance from the parent star.We study the evolution of density, radial and azimuthal velocity, and angularmomentum loss rate of equatorial decretion disks out to very distant regions.We investigate how the physical characteristics of the disk depend on thedistribution of temperature and viscosity. We calculated stationary modelsusing the Newton-Raphson method. For time-dependent hydrodynamic modeling wedeveloped the numerical code based on an explicit finite difference scheme onan Eulerian grid including full Navier-Stokes shear viscosity. The sonic pointdistance and the maximum angular momentum loss rate strongly depend on thetemperature profile and are almost independent of viscosity. The rotationalvelocity at large radii rapidly drops accordingly to temperature and viscositydistribution. The total amount of disk mass and the disk angular momentumincrease with decreasing temperature and viscosity. The time-dependentone-dimensional models basically confirm the results obtained in the stationarymodels as well as the assumptions of the analytical approximations. Includingfull Navier-Stokes viscosity we systematically avoid the rotational velocitysign change at large radii. The unphysical drop of the rotational velocity andangular momentum loss at large radii (present in some models) can be avoided inthe models with decreasing temperature and viscosity.
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