Dynamo and Hydromagnetic LiquidMetal Experiments

Magnetic dynamo experiments are being performed in many laboratories throughout the world. The most successful have been at Kalsruhe and Riga where liquid sodium has been forced in constrained flows and produced predicted postive dynamo gain. The unconstrained flows are being investigated at Wisconsin, Cadarache , and Maryland. These experiments have not reached the critical values of the magnetic Reynolds number, Rm, necessary for dynamo gain, despite the positive predictions of laminar flow theory. Experiments in understanding the relationship of turbulence to MHD are being performed in addition to these at Perm, Princeton, and Swarthmore. A naturally constrained dynamo, using angular momentum gradient, Couette flow, to suppress turbulence is being attempted at New Mexico Tech. Flow constrained by ridged walls is likely to have less turbulence than unconstrained flow where the criterion of constraint is the degree of suppression of the Helmholtz shear flow instability. The study of MHD in conjuction with fluid turbulence has become of major importance in dynamo experiments as well as to future dynamo theory. c ©0000 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim