Experiments of highly transient thermo-fluid dynamic phenomena in He II induced by gas dynamic shock wave impingement

摘要

Compression and thermal shock waves are generated in the superfluid shock tube facility by the impingement of a gas-dynamic shock wave propagating through helium vapor onto a He II free surface. He II can be shock-compressed to convert to He I across the λ-line in the case of He II initially at temperatures rather close to the λ-temperature. The phenomena realized in the shock tube are extremely rapid ones with a characteristic time of the order of a few microseconds. Accordingly, some advanced experimental technology is required for the measurement, and thus piezo-type pressure transducers and a superconductive temperature sensor are used for the measurement of the transient behavior. Visualization of both shock waves is successfully carried out by using ultra-high-speed video camera with Schlieren optics. It is found from the mass velocity of bulk He II derived from a series of video images than an high Reynolds number flow, about 1.2 * 10~7, can be realized behind a compression shock wave in a very short duration. It is also an objective of the present research to make a successful transfer of experimental techniques developed in conventional thermo-fluid dynamics to cryogenic researches.