Hydromagnetic Stability of Flow Between Rotating Cylinders

The flow of an electrically conducting fluid was studied using the rotating-cylinder viscometer technique. The device is composed of concentric cylinders immersed in mercury. The inner cylinder is driven, while a torque is transmitted to the outer cylinder until the motion due to mercury is balanced. The effective viscosity of the flujd, which is proportional to the product of the torque and the period of rotation of the inner cylinder, is measured as a function of rotational speed. This curve shows a distinct change in slope at the critical rotation rate. The experimental results are plotted in comparison with theoretical by perfectly conducting cylinders and insulating cylinders showing the relations of the critical Taylor number T/sub c/ and Q. (B.O.G.)