Schoepe, W. and Hanninen, R. and Niemetz, M. (2015) Breakdown of Potential Flow to Turbulence Around a Sphere Oscillating in Superfluid He Above the Critical Velocity. JOURNAL OF LOW TEMPERATURE PHYSICS, 178 (5-6). pp. 383-391. ISSN 0022-2291, 1573-7357
Full text not available from this repository. (Request a copy)Abstract
The onset of turbulent flow around an oscillating sphere in superfluid He is known to occur at a critical velocity where is the circulation quantum and is the oscillation frequency. But it is also well known that initially in a first up-sweep of the oscillation amplitude, can be considerably exceeded before the transition occurs, thus leading to a strong hysteresis in the velocity sweeps. The velocity amplitude where the transition finally occurs is related to the density of the remanent vortices in the superfluid. Moreover, at temperatures below ca. 0.5 K and in a small interval of velocity amplitudes between and a velocity that is about 2 % larger, the flow pattern is found to be unstable, switching intermittently between potential flow and turbulence. From time series recorded at constant temperature and driving force, the distribution of the excess velocities is obtained and from that the failure rate. Below 0.1 K we also can determine the distribution of the lifetimes of the phases of potential flow. Finally, the frequency dependence of these results is discussed.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | VIBRATING-WIRE; LAMINAR; MICROSPHERE; Quantum turbulence; Oscillatory flow; Intermittent switching; Remanent vorticity |
| Subjects: | 500 Science > 530 Physics |
| Divisions: | Physics > Institute of Experimental and Applied Physics > Alumni or Retired Professors > Prof. Wilfried Schoepe |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 24 Jul 2019 09:19 |
| Last Modified: | 24 Jul 2019 09:19 |
| URI: | https://pred.uni-regensburg.de/id/eprint/5940 |
Actions (login required)
 |
View Item |
