Linear Irreversible Thermodynamics and Super fluid He-II

Liquid helium-II, The phase of he below the -point () displays the intriguing property of superfluidity, the capacity to flow without viscous resistance (e.g.Reppy and Depatie, 1964). Howerer, He-II is capable of viscous flow at the same time, which is showin by experiments using oscillating disks (Donnelly and Robert. 1974). vibrating wires (Tough, Mccormick and Dash, 1963) and rotating viscometers (Woods and Hallett, 1963). This unusual dual behviour and many of the other transport properties of He-II have been accunted for within the phenomenological two-fluid model, which was put forward by landau and london independentty. In this model liquid helium-II is considered to be compsed of two mutually interpenetrating fluids. each with its own density and, to a first approximation, its own independent velocity fried.