Four Regimes of Decaying Grid Turbulence in a Finite Channel

Attenuation of second sound in helium II has been used to observe up to 6 orders of magnitude of decaying vorticity displaying four distinctly different regimes of decaying grid turbulence in a finite channel. A purely classical spectral model for homogeneous and isotropic turbulence describes most of the decay of helium II vorticity in the temperature range $1.2<T<\mathrm{}2\mathrm{}$ K. The four regimes switch successively as the energy-containing and dissipative Kolmogorov length scales gradually grow during the decay, finally both being saturated by the size of the channel.