Evolution of superfluid turbulence in thermal counterflow

Abstract

Using two complementary techniques, we have for the first time determined the full evolution of superfluid turbulence in a single circular tube. Our analysis shows that the evolution of the turbulence from laminar flow through the two turbulent states T I and T II is independent of the tube size and is probably a generic feature of the circular geometry. This important result finally allows a reliable comparison to be made of data from wide and narrow tube experiments. The parameters of states T I and T II are found to be well defined by these experiments, and comparison to the theory of Schwarz suggests that the fully developed state T II is reasonably homogeneous. The transition from laminar flow to state T I is consistent with previous results showing a critical density of quantized vortex lines in the turbulence. Our analysis suggests that this concept may be extended to the transition from T I to T II. Associated with this second transition is an intrinsic relaxation time that appears to diverge at the critical velocity.