Turbulent statistics and intermittency enhancement in coflowing superfluid He 4

The large-scale turbulent statistics of mechanically driven superfluid He-4 was shown experimentally to follow the classical counterpart. In this paper, we use direct numerical simulations to study the whole range of scales in a range of temperatures T is an element of [1.3,2.1] K. The numerics employ self-consistent and nonlinearly coupled normal and superfluid components. The main results are that (i) the velocity fluctuations of normal and super components are well correlated in the inertial range of scales, but decorrelate at small scales. (ii) The energy transfer by mutual friction between components is particulary efficient in the temperature range between 1.8 and 2K, leading to enhancement of small-scale intermittency for these temperatures. (iii) At low T and close to T-lambda, the scaling properties of the energy spectra and structure functions of the two components are approaching those of classical hydrodynamic turbulence.