Buoyancy-driven convection with a uniform magnetic field. Part 2. Experimental investigation

Abstract

In this paper, an experimental study of laminar magnetohydrodynamic (MHD) buoyancy-driven flow in a cylindrical cell with axis horizontal is described. A steady uniform magnetic field is applied vertically to the mercury-filled cell, which is also subjected to a horizontal temperature gradient. The main features of this internal MHD thermogravitational flow are made experimentally evident from temperature and electric potential measurements. Whatever the level of convection, raising the Hartmann number Ha to a value of the order of 10 is sufficient to stabilize an initially turbulent flow. At much higher values of the Hartmann number (Ha∼100) the MHD effects cause a change of regime from boundary-layer driven to core driven. In this latter regime an inviscid inertialess MHD core flow is bounded by a Hartmann layer on the horizontal cylindrical wall and viscous layers on the endwalls. Since the Hartmann layer is found to stay electrically inactive along the cell, the relevant asymptotic (Ha[Gt ]1) laws for velocity and heat transfer are found from the balance between the curl of buoyancy and Lorentz forces in the core, together with the condition that the flow of electric current between core and Hartmann layer is negligible. A modified Rayleigh number RaG/Ha2, which is a measure of the ratio of thermal convection to diffusion when there is a balance between buoyancy and Lorentz forces, is the determining parameter for the flow.

Numerical stability analysis and flow simulation of lid-driven cavity subjected to high magnetic field

“…The stabilisation due to the external magnetic field in the cavity has also been studied [14,15,16]. Deeper investigations have been done on the natural convected cavity under an external magnetic field both numerically [17,18,19,20] and experimentally [21]. At the best of our knowledge, the flow behaviour at high Stuart number has not been object of studies.…”

Solidified Structure Control of Metallic Materials by Static High Magnetic Fields

“…Following this attempt, numerous studies were carried out on understanding the mechanism of such effect and its operating parameters using both the numerical simulation [3][4][5][6][7][8] and experimental [9][10][11][12][13][14][15][16] methods. This understanding led to various techniques to improve the quality of the crystal which has an electroconducting or partially electroconducting nature using a magnetic field.…”

Velocity Measurement Techniques for Liquid Metal Flows

“…When the fluid flow becomes quasi-2D in a sufficiently high magnetic field, the electric potential does not vary considerably, neither in the core nor in the Hartmann layers. Davoust et al [32] and Messadek and Moreau [33] acquired velocities non-invasively at the Hartmann wall by means of electrodes mounted in the wall. These measurements yielded to a good approximation the core velocity values in planes perpendicular to the applied field.…”

“…It depends on the particular choice of geometry, the number of electrodes, and the materials thereof whether the fluid velocity is measurable without thermoelectric disturbances or the temperature can be measured in addition. Examples for such combined probes are to be found in [23,31,32].…”