  We investigate the analogy between circumstellar disks and the Taylor-Couette
flow. Using the Reynolds similarity principle, the analogy results in a number
of parameter-free predictions about stability of the disks, and their turbulent
transport properties, provided the disk structure is available. We discuss how
the latter can be deduced from interferometric observations of circumstellar
material. We use the resulting disk structure to compute the molecular
transport coefficients, including the effect of ionization by the central
object. The resulting control parameter indicates that the disk is well into
the turbulent regime. The analogy is also used to compute the effective
accretion rate, as a function of the disk characteristic parameters (orbiting
velocity, temperature and density). These values are in very good agreement
with experimental, parameter-free predictions derived from the analogy. The
turbulent viscosity is also computed and found to correspond to an
$\alpha$-parameter $2\times 10^{-4}<\alpha<2\times 10^{-2}$. Predictions
regarding fluctuations are also checked: luminosity fluctuations in disks do
obey the same universal distribution as energy fluctuations observed in a
laboratory turbulent flow. Radial velocity dispersion in the outer part of the
disk is predicted to be of the order of 0.1 km/s, in agreement with available
observations. All these issues provide a proof of the turbulent character of
the circumstellar disks, as well as a parameter-free theoretical estimate of
effective accretion rates.
