In this paper, the velocity profile of the normal component in the stationary flow of turbulent superfluid helium inside a cylindrical channel is determined, making use of a one-fluid model with internal variables \ud
derived from Extended Thermodynamics. In the hypothesis of null barycentric velocity of the fluid (the so-called counterflow situation) it is seen that, in the presence of a sufficiently high vortex length density, the velocity profile of the normal component becomes very flat in the central region of the channel.\ud
Thus, a central flat profile of the normal fluid does not necessarily imply that the flow of the normal component is turbulent
We investigate the evolution equation for the average vortex length per unit volume L of superfluid turbulence in inhomogeneous flows. Inhomogeneities in line density L and in counterflow velocity V may contribute to vortex diffusion, vortex formation and vortex destruction. We explore two different families of contributions: those arising from a second order expansion of the Vinen equation itself, and those which are not related to the original Vinen equation but must be stated by adding to it second-order terms obtained from dimensional analysis or other physical arguments.
In systems with charged mobile defects, application of an external electric field modifies the spatial distribution of defects. We obtain the corresponding dependence of the thermal conductivity on the electric field due to the redistribution of defects, both in bulk systems (heat transfer described by Fourier’s law) and in nanosystems (heat transfer described by phonon hydrodynamics). We consider the electric field transverse to the heat flux as well as the electric field parallel to the heat flux; in the latter case, we consider a superlattice composed of alternating layers with defects and without defects. For transverse electric fields, the effective thermal conductivity is increased in bulk systems and decreased in nanosystems. This dependence on the field would allow us to control heat transport in an easy and reversible way without modifying the material.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.