Turbulence in the annular flow of a conducting fluid in a magnetic field

A. V. Volkov - M. M. Gurfink - A. P. Poluektov

Abstract
A metal flow is created by the passage of a radial electric current through a liquid metal in the annular space between coaxial electrodes and by the application of an axial magnetic field. The channel has a width of 17 mm, a depth of 16 mm, and an average radius of 34 mm. A measurement of the radial distribution of the average velocity by means of conduction probes shows that within the error limits the distribution depends only on the product BI, where I is the current and B is the magnetic field. A hot-wire anemometer is used to measure the turbulent fluctuation velocity parallel to the average-flow velocity and thus perpendicular to the magnetic field. The hot-wire probe signal is amplified and sent to a loop oscillograph; the mean-square signal amplitude is measured with a vacuum thermocouple and recorded on an electronic potentiometer tape. The Reynolds number is varied in the experiments from 3000 to 7300, and the Hartmann number from 7 to 100. The measurements show that as the field is increased the energy of the component transverse to the field varies nonmonotonically; it first decreases and then increases abruptly. The behavior of the fluctuations changes significantly, becoming more regular, almost inusoidal, as the field is increased. A further increase of the field completely laminarizes the flow.