Study of thermal shock wave in shock-compressed He II induced by gas dynamic shock wave impingement

摘要

Strong thermal shock waves induced by the impingement of a gas dynamic shock wave onto a He II free surface in the superfluid shock tube facility were investigated by measuring temperature variation with superconductive temperature sensors and by Schlieren visualization method with an ultra high-speed video camera (40,500 pictures/sec). The heat transfer from shock-compressed high temperature vapor to He II forming a thermal shock wave is considered. The temperature rise ratio of an induced thermal shock to that of an incident gas dynamic shock wave was found to be very small, as small as 0.003 at 1.80K. It is seen that the most part of the heat do not be transmitted into bulk He II because a high density quantized vortex layer is rapidly developed in a thermal boundary layer in the immediate vicinity of the vapor-He II interface. The existence of a thermal boundary layer with a large temperature gradient in which the physical state varies from supercritical helium to He II temperature and the rapid growth up to about 1 mm in thickness of the layer with such as thermal conduction process are measured with the temperature measurements. Besides, it is also found that high compressibility of He II results in formation of a dark zone near the interface region that is extended toward bulk He II.