APPARATUS FOR THE STUDY OF RAYLEIGH-BENARD CONVECTION IN GASES UNDER PRESSURE

We review the history of experimental work on Rayleigh-Benard convecti on in gases, and then describe a modern apparatus that has been used i n our experiments on gas convection. This system allows for the study of patterns in a cell with an aspect ratio (cell radius/fluid layer de pth) as large as 100, with the cell thickness uniform to a fraction of a mu m, and with the pressure controlled at the level of one part in 10(5). This level of control can yield a stability of the critical tem perature difference for the convective onset of better than one part i n 10(4). The convection patterns are visualized and the temperature fi eld can be inferred using the shadowgraph technique. We describe the f low visualization and image processing necessary for this. Some intere sting results obtained with the system are briefly summarized. (C) 199 6 American Institute of Physics.