QFS2016 Book of Abstracts

Abstracts

P3.10 Study of particle motion in He II counterflow across a wide heat flux range Mastracci Brian(1,2), Takada Suguru(3), Guo Wei(1,2) 1) National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA 2) Department of Mechanical Engineering, FAMU-FSU College of Engineering, Tallahassee, FL 32310, USA 3) National Institute for Fusion Science, Toki, Gifu 509-5292, Japan Some discrepancy exists in the results of He II counterflow experiments obtained using PIV when compared with those obtained using PTV. It is suggested that this is due to differing applied heat flux ranges. An earlier PTV experiment in our lab attempted to test this model but the applied heat flux did not actually overlap with any PIV experiments. We report a PTV study of solid D2 particle motion in counterflow, and the heat flux range overlaps that of all previous visualization studies. The observed particle velocity distribution transitions from a two-peak structure to a single peak centered at 0.5vn as the heat flux is increased. The temperature dependence of this transition is examined. helium-4 using He 2 ∗ tracer-line tracking technique J. Gao(1,2), E. Varga(3,2), W. Guo(1,2), and W. F. Vinen(4) (1) Mechanical Engineering Department, Florida State University, Tallahassee, Florida State, 32310, USA (2) National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, Florida State, 32310, USA (3) Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, Prague, Czech Republic (4) School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom A high precision flow visualization technique based on the tracking of thin lines of He 2 ∗ molecular tracers has been developed in our lab. We have applied this technique in the study of steady-state counterflow turbulence in superfluid helium-4. Besides mapping out the velocity profile in the flow channel, we can also determine turbulence statistics such as the velocity distribution functions and the structure functions based on the analysis of tracer-line mages. We report how these statistics vary with temperature and heat flux. We also discuss our on-going development of an advanced tracer-line image processing method. P3.11 Statistical measurement of counterflow turbulence in superfluid

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