  We present experimental, numerical and theoretical studies of a vortex front
propagating into a region of vortex-free flow of rotating superfluid 3He-B. We
show that the nature of the front changes from laminar through quasi-classical
turbulent to quantum turbulent with decreasing temperature. Our experiment
provides the first direct measurement of the dissipation rate in turbulent
vortex dynamics of 3He-B and demonstrates that the dissipation is temperature-
and mutual friction-independent in the T->0 limit, and is strongly suppressed
when the Kelvin-wave cascade on vortex lines is predicted to be involved in the
turbulent energy transfer to smaller length scales.
