Type of Document	Dissertation
Author	Xu, Ting
Author's Email Address	tingxu@magnet.fsu.edu
URN	etd-11052007-211835
Title	Velocity Field Measurements of He Ii Forced Flow Using the Particle Image Velocimetry Technique
Degree	Doctor of Philosophy
Department	Mechanical Engineering, Department of
Advisory Committee	Advisor Name Title Cesar A. Luongo Committee Member James S. Brooks Committee Member Justin Schwartz Committee Member Steven W. Van Sciver Committee Member
Keywords	PIV Forced Flow Hydrogen Particles PIV Superfluid Helium Forced Flow Superfluid Helium Hydrogen Particles Particle Seeding Particle Seeding
Date of Defense	2007-10-24
Availability	unrestricted
Abstract We report measurements of the velocity fields in He II forced flow obtained by the Particle Image Velocimetry (PIV) technique, a technique which uses micron scale tracer particles to track the flow. We demonstrate that the micron size solid deuterium particles are the best choice for tracing He II forced flow in a horizontal channel. A novel particle seeding device has been developed to form micron size solid hydrogen isotope tracer particles directly within a He II flow. The tracking mechanism and the fidelity of these particles have been examined and are discussed herein. He II forced flows up to 287 mm/s are created in a square cross-section visualization channel within Liquid Helium Flow Visualization Facility (LHFVF). In the adiabatic flow case, visualization results confirm the existence of the turbulent boundary layer, with the measured velocity profiles being in reasonable agreement with empirical correlations for the classical fluids. No temperature dependence to the velocity profiles is observed within the temperature range tested (1.65 K to 2.10 K). We also tested the case of thermal counterflow in the horizontal channel without net flow. Heater powers ranging from 0.4 kW/m2 to 6.6 kW/m2 were applied to the channel at two different bath temperatures, 1.80 K and 1.95 K. We observe millimeter size vortices randomly located in the transient velocity field as measured by the tracer particles. The mean velocity results confirm that the tracer particles do not exactly track the normal fluid component motion, an effect which was observed by previous researchers with vertically oriented thermal counterflow channels. No turbulent boundary layer is observed in this case. A quantitative comparison with previous research in this area is also presented. Finally, we examine forced flow He II with constant applied heat flux, in which the forced flow is coupled with the thermal counterflow. In this case, the measured particle velocity fields show a similar flow pattern as the adiabatic case and the turbulent boundary layer remains. The mean velocity of the tracer particles is seen to be greater than the flow velocity and increases linearly with the normal fluid velocity; however, the rate of increase is less than predicted based on the two-fluid model. Observing and quantifying He II flow velocity fields can extend our knowledge of He II fundamentals and facilitate the refining of existing He II fluid dynamics models.
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