Visualization studies of forced flow liquid helium

Florida State University, Tallahassee FL

Investigators

Abstract

Title: Visualization studies of forced flow liquid helium PI: Steven W. Van Sciver, FSU Co-PI: Sylvie Fuzier, FSU We undertake an experimental research effort to develop and apply Particle Image Velocimetry (PIV) techniques to the fundamental study of fluid dynamic processes in high Reynolds number, forced flow liquid helium. This work is of interest because liquid helium is an exceptional fluid with exceptional properties. In particular, helium has two liquid phases: He I, a near classical fluid existing at temperatures between Tc = 5.2 K and T = 2.176 K, and He II or superfluid helium below T, which is a quantum fluid. He II displays thermal fluid properties not seen in any other fluid. Many of these properties provide benefits to the operation of large-scale, low temperature technologies such as superconducting magnets and accelerators. Although the fluid dynamic processes in liquid helium have been extensively studied by conventional macroscopic techniques like pressure and temperature measurement, only very recently have there been attempts to investigate the micro-scale phenomena that underpin these processes. Such phenomena are best explored using modern flow diagnostic techniques such as PIV. Advancing our basic, micro-scale understanding of liquid helium fluid dynamics represents the principal intellectual merit of the proposed project. The work is mainly experimental in nature, and is aimed at visualizing flow phenomena in both He I and He II. Two configurations will be studied: duct flow and flow around bluff bodies such as cylinders or spheres contained in a duct with flow velocities up to about 0.5 m/s (corresponding to Reynolds numbers in the range of 105 to 106). One of the expected outcomes is the first-ever observation of the velocity boundary layer in He I and He II. Subsequently, cylinders and other bluff bodies will be placed in the flow channel and the conditions around the body studied again using PIV. In the broader context, liquid helium has the lowest viscosity of any condensed fluid and thus brings to fluid dynamics and heat transfer studies the ability to achieve very high Reynolds number in moderate size systems. Such benefits have inspired a number of laboratories world-wide to establish high Reynolds number fluid dynamics facilities using liquid helium. However, previous PIV studies in He II in particular have shown that the interaction between the suspended particles and the liquid may be more complex than assumed. Thus, one of the broader impacts of the project will be through improving the understanding of PIV measurement techniques for liquid helium systems so that they useful to all researchers in the field. In addition to these technical developments, the proposed program should also have a significant impact on the educational experience of engineering students, including those from under represented groups. In addition to the graduate student PIV research effort described in the proposal, we will also craft several smaller scale projects suitable for undergraduate student participation through the Senior Design class in the M E Department of the FAMU-FSU College of Engineering or for summer students recruited through the REU/RET program at the nearby National High Magnetic Field Laboratory. This unique opportunity will provide these individuals with a research or design experience unattainable anywhere else in the US; an experience that may lead to a career in the field of cryogenics.