Decay of Two-Dimensional Superfluid Turbulence over Pinning Surface

Area of Science:

• Fluid dynamics
• Quantum turbulence
• Superfluidity

Background:

• Quasi-two-dimensional turbulence in superfluids is crucial for understanding quantum phenomena.
• Nanofluidic confinement introduces unique boundary effects on fluid behavior.
• Vortex dynamics in superfluids are complex and influenced by various factors.

Purpose of the Study:

• To investigate the free decay of quasi-two-dimensional turbulence in superfluid ⁴He within nanofluidic channels.
• To characterize the vortex density decay and identify governing mechanisms.
• To compare experimental results with a numerical model.

Main Methods:

• Utilized a pump-probe technique to observe vortex density decay.
• Confined superfluid ⁴He in quasi-two-dimensional nanofluidic channels.
• Developed a numerical model incorporating velocity-dependent effective mutual friction to simulate vortex pinning.

Main Results:

• Observed a complex vortex density decay deviating from a simple power law.
• Identified a universal fast transient decay (L∝t^{-2}) followed by a slower, nonuniversal regime.
• Demonstrated that decay is governed by vortex pinning on channel walls and probe flow effects.

Conclusions:

• The decay dynamics are dictated by the interplay between vortex pinning and flow mobilization.
• The developed numerical model successfully replicates key experimental observations.
• Findings provide insights into quantum turbulence in confined geometries.