Flow of the normal component of He-II about bluff objects observed with He*2 excimers

Flow of the normal fluid component of He II about a cylinder and flat plate in a channel with a square crosssection was observed by tracking clouds of He*2 excimers. Flow was produced using a lithographically patterned heater. The direction and speed of flow projected onto a plane parallel to the axis of the channel and perpendicular to the heater exhibited significant change with time even after the heater was turned off. Flow was recorded in movies. Excimers moved at least as fast as could be recorded by the camera. Velocity vector field maps of flow suggest formation of structures downstream of the cylinder object that are consistent with parts of eddies. In this paper, we establish a foundation to observe normal component flow of a quantum fluid over centimeters.

Automated summary

The flow of the normal fluid component of He II around a cylinder and flat plate in a channel with a square crosssection was observed using He*2 excimer clouds tracking. The flow was generated by a lithographically patterned heater, and even after the heater was turned off, the direction and speed of the flow exhibited significant changes over time. High-speed movies were recorded to capture the fast movement of excimers. Velocity vector field maps indicated the formation of structures downstream of the cylinder that resembled eddies. This paper establishes a foundation for the observation of normal component flow in a quantum fluid over centimeters.