Accretion and effluxion of mass and angular momentum

The hydrodynamical accretion and effiuxion of isentropic or isothermal material with uniform specific angular momentum, L sin θ, is solved exactly on a stream line, θ = constant. The critical value for L, Lm(γ), above which accretion is severely curtailed and effiuxion is rotationally driven, is found as the principal new result. This critical value appears as the maximum L for which Venturi flow (i.e. with a choke point) occurs. The accretion-effiuxion rate, A, and the location of the choke point, R, are given exactly for the Venturi curves as a function of L. The topology of the solutions is shown to include a vortex (elliptic) point as well as a choke (hyperbolic) point, and the figures display this behaviour explicitly.