AbstractWe consider accretion onto a two–dimensional polytropic tube. In contrast to the standard papers we apply spatially uniform eddy viscosity (and eddy conductivity in part II resp.). In principle, the resulting rotation law is non–keplerian and proves to be rather flat. Wether the angular velocity increases or decreases inwadly depends on the strength of the torque exerted on the outer surface which is due to the inflow of angular momentum. Large (small) torque cause super–(sub–)rotation. The frictionally originated luminosity varies for various models. It lies one or two orders of magnitude below the total avialable accretion energy. For certain combinations of the Mach numbers the radial inflow profile possesses a soni