2012/02/03 by Julien Salort, Benoît Chabaud, Emmanuel Lévêque +1 · 1 citation
Physics and Astronomy · #physics.flu-dyn #cond-mat.quant-gas #cond-mat.stat-mech
paper · pdf · doi:10.1209/0295-5075/97/34006
published as EuroPhysics Letters : EPL 97 (2012) 34006 · 6 pages, 7 figures
arxiv created 2012/02/03 · arxiv updated 2012/02/06
The 4/5-law of turbulence, which characterizes the energy cascade from large to small-sized eddies at high Reynolds numbers in classical fluids, is verified experimentally in a superfluid 4He wind tunnel, operated down to 1.56 K and up to Rlambda ~ 1640. The result is corroborated by high-resolution simulations of Landau-Tisza's two-fluid model down to 1.15 K, corresponding to a residual normal fluid concentration below 3 % but with a lower Reynolds number of order Rlambda ~ 100. Although the Kármán-Howarth equation (including a viscous term) is not valid a priori in a superfluid, it is found that it provides an empirical description of the deviation from the ideal 4/5-law at small scales and allows us to identify an effective viscosity for the superfluid, whose value matches the kinematic viscosity of the normal fluid regardless of its concentration.