Search results for " counterflow"
showing 6 items of 6 documents
Alternative Vinen equation and its extension to rotating counterflow superfluid turbulence
2007
Two alternative Vinen's evolution equations for the vortex line density L in counterflow superfluid turbulence, are physically admissible and lead to analogous results in steady states. In Phys. Rev. B, 69, 094513 (2004) the most used of them was generalized to counterflow superfluid turbulence in rotating containers. Here, the analogous generalization for the alternative Vinen's equation is proposed. Both generalized Vinen's equations are compared with the experimental results, not only in steady-states but also in some unsteady situations. From this analysis follows that the solutions of the alternative Vinen's equation tend significantly faster to the corresponding final steady state val…
Non-equilibrium thermodynamics analysis of rotating counterflow superfluid turbulence
2010
In two previous papers two evolution equations for the vortex line density $L$, proposed by Vinen, were generalized to rotating superfluid turbulence and compared with each other. Here, the already generalized alternative Vinen equation is extended to the case in which counterflow and rotation are not collinear. Then, the obtained equation is considered from the viewpoint of non-equilibrium thermodynamics. According with this formalism, the compatibility between this evolution equation for $L$ and that one for the velocity of the superfluid component is studied. The compatibility condition requires the presence of a new term dependent on the anisotropy of the tangle, which indicates how the…
Non-classical Velocity Statistics in Counterflow Quantum Turbulence
2014
In this work we analyse the statistical distribution of turbulent superfluid velocity components in a He II counterflow channel, via two-dimensional numerical simulations pre- sented in past studies. The Probability Density Functions (PDFs) of the superfluid velocity components are investigated at lengthscales smaller than the average intervortex spacing, for varying vortex densities and different wall-normal distances. The results obtained con- firm the non-classical signature of quantum turbulence already observed in past numerical studies.
Non-Equilibrium Thermodinamic analysis of rotating counterflow superfluid turbulence
2008
Two alternative evolution equations for the vortex line density L in counterflow superfluid turbulence in 4He were proposed by Vinen in 1958. These equations was recently generalized to counterflow superfluid turbulence in rotating containers. Here, according with the formalism of Non-Equilibrium Thermodynamics, the compatibility between the alternative Vinen equation as evolution equation for the vortex line density in rotating counterflow turbulence and the velocity of the superfluid component is studied. From the compatibility request a new term dependent on the anisotropy of the tangle arises.
Vortex dynamics in rotating counterflow and plane Couette and Poiseuille turbulence in superfluid Helium
2008
An equation previously proposed to describe the evolution of vortex line density in rotating counterflow turbulent tangles in superfluid helium is generalized to incorporate nonvanishing barycentric velocity and velocity gradients. Our generalization is compared with an analogous approach proposed by Lipniacki, and with experimental results by Swanson et al. in rotating counterflow, and it is used to evaluate the vortex density in plane Couette and Poiseuille flows of superfluid helium.