title: Visualization study of counterflow in superfluid 4He using metastable helium molecules.
abstract: 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.
authors.affiliation: Physics Department, Yale University, New Haven, Connecticut 06515, USA.
authors.forename: W
authors.initials: W
authors.lastname: Guo
authors.forename: S B
authors.initials: SB
authors.lastname: Cahn
authors.forename: J A
authors.initials: JA
authors.lastname: Nikkel
authors.forename: W F
authors.initials: WF
authors.lastname: Vinen
authors.forename: D N
authors.initials: DN
authors.lastname: McKinsey