423 research outputs found
Evolution of a Network of Vortex Loops in the Turbulent Superfluid Helium; Derivation of the Vinen Equation
The evolution a network of vortex loops due to the fusion and breakdown in
the turbulent superfluid helium is studied. We perform investigation on the
base of the "rate equation" for the distribution function of number of
loops in space of their length . There are two mechanisms for change of
quantity . Firstly, the function changes due to deterministic process of
mutual friction, when the length grows or decreases depending on orientation.
Secondly, the change of occurs due to random events when the loop
crosses itself breaking down into two daughter or two loops collide merging
into one larger loop. Accordingly the "rate equation" includes the "collision"
term collecting random processes of fusion and breakdown and the deterministic
term. Assuming, further, that processes of random colliding are fastest we are
in position to study more slow processes related to deterministic term. In this
way we study the evolution of full length of vortex loops per unit volume-so
called vortex line density . It is shown this evolution to obey
the famous Vinen equation. In conclusion we discuss properties of the Vinen
equation from the point of view of the developed approach.Comment: Presentation at QFS2006, submitted to JLT
Vortex density waves and high-frequency second sound in superfluid turbulence hydrodynamics
In this paper we show that a recent hydrodynamical model of superfluid
turbulence describes vortex density waves and their effects on the speed of
high-frequency second sound. In this frequency regime, the vortex dynamics is
not purely diffusive, as for low frequencies, but exhibits ondulatory features,
whose influence on the second sound is here explored.Comment: 8 page
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