2025/10/31 by Filip Novotný, Marek Talíř, Novotný, Filip +5
Engineering · Physics and Astronomy · #Atomic and Subatomic Physics Research #FOS: Physical sciences #Fluid Dynamics (physics.flu-dyn) #Fluid dynamics and aerodynamics studies #Quantum, superfluid, helium dynamics
paper · pdf · doi:10.48550/arxiv.2510.27440
openalex publication_date 2025/10/31 · openalex created_date 2025/11/05 · openalex updated_date 2026/07/30
Horizontally (\mathbfΩ ⊥ v_\rmns) and axially (\mathbfΩ ∥ v_\rmns) rotating counterflow of superfluid 4He (He~II) generated thermally in a square channel is studied using the second sound attenuation technique, detecting statistically steady state and temporal decay of the density of quantized vortex lines L(t,Ω). The array of rectilinear quantized vortices created by rotation at angular velocity Ω strongly affects the transient regimes of quantum turbulence characterized by counterflow velocity v_\rmns, differently in both geometries. Two effects are observed, acting against each other and affecting the late temporal decay L(t,Ω). The first is gradual decrease of the decay exponent μ of the power law L(t,Ω) ∝ t-μ, associated with the fact that under rotation thermal counterflow acquires two-dimensional features, clearly observed and recently reported by us (Phys. Fluids 36, 105121 (2024)) in the \mathbfΩ ∥ v_\rmns geometry. It exists in the \mathbfΩ ⊥ v_\rmns geometry as well, however, it is screened here by the influence of the effective Ekman layer built within the effective Ekman time of order seconds. For faster rotation rates L(t,Ω) gradually ceases to display a clear power law. Instead, rounded and ever steeper decays occur, gradually shifted toward shorter and shorter times, significantly shortening the time range for a possible self-similar decay of vortex line density. This effect is not observed in \mathbfΩ ∥ v_\rmns geometry, as here the much longer effective Ekman time of order minutes cannot affect the observed L(t,Ω) decay appreciably.