Turbulent cascade of a quantum fluid at finite temperature

Emmanuel Lévêque (1) , Carlo Barenghi (2) , Pantxo Diribarne (3) , Philippe-Emmanuel Roche (4)

1 Phys-ENS - Laboratoire de Physique de l'ENS Lyon
2 School of Mathematics and Statistics
3 SBT - Service des Basses Températures
4 NEEL - HELFA - Hélium : du fondamental aux applications

The turbulent inertial cascade undergone by a quantum fluid at small but finite temperature above absolute zero is simulated by DNS of 2 coupled Navier-Stokes equations. Following the 2-fluid model of Landau and Tisza, one equation accounts for the viscous normal fluid, while the other equation models the superfluid dynamics on scales larger than the inter-vortex spacing. An artificial superfluid viscosity is introduced - as a turbulence closure - to model non-viscous processes taking place on scales smaller than the inter-vortex spacing, such as phonon emission. Three outcomes are presented. The first is the strong locking of the superfluid and normal fluid along the turbulent cascade, including the overlapping of the vorticity structures. The second is the peaking at small scales of the residual slip velocity between the two fluids. The third is a temperature dependence of the Reynolds number - defined using the separation of large and small scales. We argue that these three features evidenced in the simulations should also be present in real turbulent quantum fluids.

Domaines: Autre [cond-mat.other]

Emmanuel Lévêque, Carlo Barenghi, Pantxo Diribarne, Philippe-Emmanuel Roche. Turbulent cascade of a quantum fluid at finite temperature. 12th EUROMECH European Turbulence Conference, Sep 2009, Marburg, Germany. pp.281-284, ⟨10.1007/978-3-642-03085-7_68⟩. ⟨hal-00430190⟩