Publikace na Matematicko-fyzikální fakulta |
2012
Abstrakt
We present measurements of the drag forces on quartz tuning forks oscillating at low velocities in normal and superfluid He-4. We have investigated the dissipative drag over a wide range of frequencies, from 6.5 to 600 kHz, by using arrays of forks with varying prong lengths and by exciting the forks in their fundamental and first overtone modes.
At low frequencies the behavior is dominated by laminar hydrodynamic drag, governed by the fluid viscosity. At higher frequencies acoustic drag is dominant and is described well by a three-dimensional model of sound emission.