Video: Demonstration of the thermal edge flow in a rarefied gas

Abstract

The video files are the digitized version of video films chosen from the video records in the course of the experimental work published in 1997 (Y. Sone and M. Yoshimoto, Phys. Fluids 9, 3530－3534). In the experiment, it is demonstrated by a small windmill that a flow is induced near the edge of uniformly heated rectangular plate in a rarefied gas in such a way that a gas in front of the edge of the plate is pulled in along the plate, which is now called thermal edge flow. The experiment is done in a vacuum chamber in a glass bell jar, where the pressure can be controlled between the atmospheric pressure and several pascals. In Video 1, with decrease of the pressure in the chamber, a horizontal flow is shown to be induced in such a way as for a gas in front of the vertical edge of the heated plate set vertically in the chamber to be pulled in along the plate. In Video 2, a vertical flow around the upper horizontal edge of the heated plate set vertically is shown. Here, with decrease of the pressure in the chamber, transition from an upward natural convection to a downward thermal edge flow is seen by the reversal of the direction of rotation of the windmill.