Visualization study of counterflow in superfluid 4He using metastable helium molecules.
Heat is transferred in superfluid 4He via a process known as thermal counterflow. It has been known for many years that above a critical heat current the superfluid component in this counterflow becomes turbulent. It has been suspected that the normal-fluid component may become turbulent as well, but experimental verification is difficult without a technique for visualizing the flow. Here we report a series of visualization studies on the normal-fluid component in a thermal counterflow performed by imaging the motion of seeded metastable helium molecules using a laser-induced-fluorescence technique. We present evidence that the flow of the normal fluid is indeed turbulent at relatively large velocities. Thermal counterflow in which both components are turbulent presents us with a theoretically challenging type of turbulent behavior that is new to physics.
Guo
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W
Physics Department, Yale University, New Haven, Connecticut 06515, USA.
Cahn
S B
SB
Nikkel
J A
JA
Vinen
W F
WF
McKinsey
D N
DN