  In this short paper we show that making turbulence two- rather than
three-dimensional may increase effective turbulent viscosity by about 40%.
Dimensionless hydrodynamical viscosity parameter up to \alpha\_{max} = 0.25
M_t^2 may be obtained in this approach, that is in better agreement with the
observational data on non-stationary accretion than the values obtained in
numerical simulations. However, the \alpha-parameter values known from
observations are still several times higher.
