ArticlePhys Fluids. 2017, Vol. 29, p. 105108. DOI: 10.1063/1.4991558
- Publication URL https://doi.org/10.1063/1.4991558
- Abstract The intermittency of turbulent superfluid helium is explored systematically in a steady wake flow from 1.28 K up to T>2.18K using a local anemometer. This temperature range spans relative densities of superfluids from 96 down to 0, allowing us to test numerical predictions of enhancement or depletion of intermittency at intermediate superfluid fractions. Using the so-called extended self-similarity method, scaling exponents of structure functions have been calculated. No evidence of temperature dependence is found on these scaling exponents in the upper part of the inertial cascade, where turbulence is well developed and fully resolved by the probe. This result supports the picture of a profound analogy between classical and quantum turbulence in their inertial range, including the violation of self-similarities associated with inertial-range intermittency.
ArticleEPL. 2012, Vol. 97, p. 34006. DOI: 10.1209/0295-5075/97/34006
- Publication URL https://doi.org/10.1209/0295-5075/97/34006
- Abstract 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 Rλ≈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 Rλ≈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.