Quantum Turbulence

QUANTUM TURBULENCE : DECAY OF GRID
TURBULENCE IN A DISSIPATIONLESS FLUID We produced grid
turbulence in liquid helium at 520 mK to compare with
classical experiments and theories. Above T = 1 K, with
viscosity present, it has been shown that grid turbulence is
equivalent to homogeneous isotropic turbulence in a
classical fluid. We seek to investigate the nature of grid
turbulence when viscosity is zero. Specifically, in the
absence of viscosity in a quantum fluid, through what path
does the turbulence decay? To produce grid turbulence, a
magnetically shielded superconducting linear motor was
designed and built to accelerate and decelerate the grid
rapidly in a short distance (~ 1 mm), and achieve glide
speeds up to 1 m/s, when driven with the properly shaped
current pulse. We measured the decay of the turbulence
produced by calorimetry technique. Recent theory suggests
the decay occurs through a Kelvin-wave cascade on the vortex
lines which couples the initially large turbulent eddies to
the short wavelength phonon spectrum of the liquid, yielding
a characteristic rate of temperature rise. Initial
measurements support the Kelvin wave cascade theory.