With this experiment we study turbulence in He II using direct flow visualization and second sound attenuation. The characteristics of thermally generated flow are important since He II is used as a coolant for superconductors and spacebased instrumentation. Researchers are interested in understanding mechanically generated turbulence in cryogenic helium because this fluid has low kinematic viscosity, which may allow it to emulate large scale flow in a compact and efficient laboratory setting.
This experiment is conducted in a 13 in. long transparent vertical flow channel with 5/8 x 5/8 in. cross section submersed in a helium cryostat with optical access. Flow can be generated using the heater at the bottom of the channel or by towing a mesh grid (mesh number M = 3, 3.75, or 5 mm) through the channel at speeds up to 1 m/s. Images of the resulting flow can be captured at a rate up to 120 frames per second.