Superfluid turbulence: Experiments, physical principles, and outstanding problems

The paper provides an introduction to turbulence in a superfluid (quantum turbulence), with special reference to cases where there is a simple classical analogue. The important experiments are described briefly, together with the most plausible interpretations. The quantum and classical cases are, compared, similarities and differences in the underlying physical principles being emphasized. Outstanding problems axe. summarized. A more detailed discussion of the issues raised can be found in a recent review: W F Vinen and J J Niemela, J. Low Temp. Phys. 128, 167 (2002).