Sidewall flow instabilities in liquid metal MHD flow under blanket relevant conditions

A flow instability has been observed in a rectangular thin conducting wall duct in MHD experiments at ANL's ALEX facility. It developed in a side layer jet attached to a side wall parallel to the applied B-field. The nature of the instability resembles very strongly that of a classic laminar instability in ordinary fluid mechanics. The phenomenon is distinguished from ordinary turbulence by its strong periodicity and its lack of small scale structure. A preliminary identification of the factors which may influence the instability has been made. For the conditions and test section geometry reported here, the instability appears at an approximately constant critical Reynolds number 2650 < Re/sub cr/ < 5100, independent of Hartmann number in the range 2700 < M < 5400. 6 refs., 18 figs