Experimental Investigation of Thermal Shock Wave Induced by Gas Dynamic Shock Wave Impingement

Abstract

The thermal shock wave in He II is investigated by measuring the temperature variation with a superconductive temperature sensor. It is generated by the impingement of a gas dynamic shock wave onto a He II free surface in the newly developed superfluid shock tube facility. The profile of thermal shock is found to be of a single triangular waveform with a limited shock strength. It is suggested from the experimental result that a thermal shock wave is generated not at the moment of the impingement nor propagates from the original free surface, but it is generated at slightly lower than the original free surface and a little later than the impingement. This means that a thermal shock wave is generated at the lower end of a thermal boundary layer after it is established. In the thermal boundary layer with a thickness of several mm, the thermodynamic state changes from supercritical at the original free surface to compressed He II via compressed He I. It is sometimes found in the experiments near lambda temperatures, that no thermal shock wave is detected in shock compressed He II. It can be understood that shock compression makes He II convert to He I where no thermal shock wave is excited.