ENTRAINMENT OF SECOND SOUND IN STEADY-STATE COUNTERFLOWING NORMAL AND SUPERFLUID HELIUM 2

The velocity dependence of second sound in liquid helium was measured as a function of the relative velocity (v→n-v→s), where v→n is the normal fluid velocity and v→s is the superfluid velocity. The experimental technique consisted of measuring the time of flight of a second-sound pulse in steady-state counterflowing normal and superfluid for subcritical velocities. The results are in agreement with the theoretical predictions by Khalatnikov. © 1969 The American Physical Society.