Superfluid Helium in Three-Dimensional Counterflow Differs Strongly from Classical Flows: Anisotropy on Small Scales

Abstract

Three-dimensional anisotropic turbulence in classical fluids tends towards isotropy and homogeneity with decreasing scales, allowing -eventually-the abstract model of "isotropic homogeneous turbulence" to be relevant. We show here that the opposite is true for superfluid 4 He turbulence in 3-dimensional counterflow channel geometry. This flow becomes less isotropic upon decreasing scales, becoming eventually quasi 2-dimensional. The physical reason for this unusual phenomenon is elucidated and supported by theory and simulations. arXiv:1901.02215v1 [cond-mat.other]

Coupled dynamics of quantized vortices and normal fluid in superfluid He4 based on the lattice Boltzmann method

“…[43,44] and numerically obtained in Refs. [16,20], is also confirmed in our numerical simulation as a stripelike structure elongated in the streamwise direction (see Fig. 4 and video in Ref.…”

“…III C and IV, such ephemeral excitations are continuously created and the inhomogeneity in fluctuations remains persistently in the normal-fluid flow profile, which qualitatively agrees with phenomena reported in Refs. [16,20,43,44].…”

“…Although such preceding computational results have enabled us to understand the steady quantum turbulence quantitatively, in the majority of the early approaches, quantized vortices were considered as completely independent objects, i.e., the normal fluid velocity profile was prescribed and the vortices were influenced by the normal fluid through mutual friction, whereas the vortices did not influence the dynamics of the normal fluid. Several recent studies have addressed this issue by solving the Hall-Vinen-Bekarevich-Khalatnikov (HVBK) equations for normal fluid component [16][17][18][19][20][21][22]. The HVBK equations are essentially the Navier-Stokes (NS) equations with a forcing term ascribed to the mutual friction between the normal and superfluid components due to the motions of the quantized vortices [6].…”

A Report on influences from superfluid turbulence in Der Rufer for percussion quartet

“…The reason is that nonlinear fluid flow tends to resemble isotropy when cascading at smaller scales. However, with superfluid turbulence we move into conditions that promote quasi two-dimensional flow that will be discussed further with the property known as second sound 4 .…”

Theory of anisotropic superfluid4He counterflow turbulence

“…Although such a spectral anisotropy was predicted theoretically and confirmed numerically [29,30], the experimental investigations of the energy spectra for the time being are limited to the plane, orthogonal to the direction of the counterflow velocity [28,33], while the theory of counterflow turbulence [24] was developed assuming spectral isotropy. In this paper, we relax this assumption and offer a theoretical description of the spectral anisotropy of the energy spectra of the counterflow turbulence in superfluid 4 He.…”