Department of Applied Physics, Okayama University of Science
Abstract
The viscosity of liquid ^4He has been measured by means of a high-Q torsional oscillator at temperatures between 1.8 K and 2.8 K under saturated vapour pressure. Below the superfluid transition temperature, the eddy viscosity in addition to the viscosity caused by the normal fluid component was observed when the velocity of cell-wall exceeded the critical velocity. The magnitude of the critical velocity depends on the roughness of the cell wall. In the case of a cell with rough wall, the critical velocity is low compared with a cell with smooth wall
