Temperature effects on the evolution of quantum vortices in superfluid helium under thermal counterflow

The transient establishment of the vortex field in He II thermal counterflow is governed by the coupled effects of local vortex production-decay and spatial redistribution. A one-dimensional numerical framework based on the two-fluid model and Vinen’s equation is used to investigate transient vortex evolution over the bath temperature range from 1.6 to 2.0 K. To separate the intrinsic local initiation from spatial transport, the transport term is excluded in a simplified analysis, from which an analytical expression is derived for the time required for the initial source term to trigger rapid vortex growth. The fully coupled simulations are then used to evaluate the position dependent build-up time and the shift of the maximum vortex evolution rate caused by spatial transport. At a heat flux of q = 10000 W/m 2 , the build-up time exhibits a nonmonotonic dependence on bath temperature and reaches a minimum near 1.85 K. Comparison between the simulated and simplified evolution shows that this minimum results from the temperature dependent change in the contribution of local production-decay and spatial redistribution. The present work quantitatively describes the establishment of a spatially inhomogeneous vortex line density field.