Experiments on the Stability of Couette Motion with a Radial Thermal Gradient

An experimental study has been made of the hydrodynamic stability of viscous flow between coaxial rotating cylinders with a superposed radial thermal gradient. For the data presented, the outer cylinder is at rest and the annulus is small. The axis of the cylinders is vertical; the fluid is water. There is a qualitative difference between the type of instability which first sets in when the thermal gradient is zero or nonzero: the secondary motion when the gradient is nonzero does not consist of toroidal Taylor cells. However, there is a transition to Taylor cells at a higher Taylor number. Free convection affects the results strongly. Quantitative data concerning the transition to Taylor cells are presented along with a qualitative description of the cells which first cause instability.