Dissipation of grid turbulence in helium II

The results of a number of recent experiments on high Reynolds number grid turbulence in helium II suggest that its flow on large length scales resembles that of a classical fluid. It has been known for some time that the effective kinematic viscosity of this turbulent fluid, describing energy flow in the inertial range of wave numbers, is of the order of eta/rho where eta is the normal fluid viscosity and rho is the total density of the liquid. However, dissipation must be strongly influenced by quantum processes, and it cannot be associated simply with the normal-fluid viscosity. The importance of quantum processes arises because the dissipation occurs at small length scales, comparable with the spacing of the quantized vortex lines that allow turbulent motion in the superfluid component. We report an analysis of experimental data that allows us to deduce experimental values of the effective kinematic viscosity, which we call nu'(not equaleta/rho), to which theories of the quantum dissipative processes can be compared. (C) 2002 American Institute of Physics.