Some Experiments Regarding Dissipation in Helium Superflow

Experiments are reported on the dissipative steady-state flow regime of liquid helium II. These were done with a view to examining the theoretical assertion that the chemical potential gradient $\nabla \mu$ is related to the superfluid-flow speed $v_s$, by the equation $-\nabla \mu =G\exp \left(\frac{1-v_c\mathrm{}\left(T\right)\mathrm{}}{v_s}\right]$. Our experiments showed good qualitative agreement with this equation. Other assertions about the magnitude of the parameters in this equation and their dependence upon the superfluid fraction $\frac{{\rho }_s}{\rho }$ and temperature $T$ were also explored experimentally.