Flow Instabilities in Superfluid Helium due to Oscillating Structures EuHIT Funded Project


  • Article
    Jackson, M. J.; Kolosov, O.; Schmoranzer, D.; Skrbek, L.; Tsepelin, V.; Woods, A. J.
    Journal of Low Temperature Physics. 2016, Vol. 183, Issue 3, p. 208-214. DOI: 10.1007/s10909-015-1397-4
    • Publication URL http://dx.doi.org/10.1007/s10909-015-1397-4
    • Abstract We present proof-of-concept measurements of the vortex line density generated by a quartz tuning fork resonator probed by the attenuation of second sound in superfluid \(^{4}\)He at 1.6 K. The force–velocity response of a quartz tuning fork operating at a frequency of 31 kHz exhibited the onset of extra damping at a velocity of 0.5 ms\(^{-1}\). Attenuation of the 5th resonant mode of second sound was observed at the same velocity, indicating the production of vortex lines. Our measurements demonstrate that an increase of the drag coefficient corresponds to the development of quantum turbulence.
  • Article
    Jackson, M. J.; Tsepelin, V.; Poole, M.; Woods, A. J.; Človečko, M.; Skrbek, L.; Schmoranzer, D.
    Physical Review B. 2016, Vol. 94, Issue 21, p. 214503. DOI: 10.1103/PhysRevB.94.214503
    • Publication URL https://link.aps.org/doi/10.1103/PhysRevB.94.214503
    • Abstract We report recent investigations into the transition to turbulence in superfluid \(^{4}\)He, realized experimentally by measuring the drag forces acting on two custom-made quartz tuning forks with fundamental resonances at 6.5 kHz and 55.5 kHz, in the temperature range 10 mK to 2.17 K. In pure superfluid in the zero temperature limit, three distinct critical velocities were observed with both tuning forks. We discuss the significance of all critical velocities and associate the third critical velocity reported here with the development of large vortical structures in the flow, which thus starts to mimic turbulence in classical fluids. The interpretation of our results is directly linked to previous experimental work with oscillators such as tuning forks, grids, and vibrating wires, focusing on the behavior of purely superfluid \(^{4}\)He at very low temperatures.