Experimental study of the instability of the Hartmann layer

• Published in: Journal of fluid mechanics 2004-04, Vol.504, p.167-181
• Main Authors: MORESCO, P., ALBOUSSIÈRE, T.
• Format: Article
• Language: English
• Subjects: Earth Sciences; Exact sciences and technology; Flows in ducts, channels, nozzles, and conduits; Fluid dynamics; Fundamental areas of phenomenology (including applications); Geophysics; Magnetic fields; Magnetohydrodynamics and electrohydrodynamics; Physics; Sciences of the Universe; Transition to turbulence; Turbulent flows, convection, and heat transfer
• ISSN: 0022-1120; 1469-7645
• DOI: 10.1017/S0022112004007992

Hartmann layers are a common feature in magnetohydrodynamics, where they organize the electric current distribution in the flow and hence the characteristics of the velocity field. In spite of their importance their stability properties are not well understood, mainly because of the scarcity of experimental data. In this work we investigated experimentally the transition to turbulence in the Hartmann layers that arise in magnetohydrodynamic flows in ducts. From measurements of the friction factor a well-marked transition to turbulence was found at a critical Reynolds number, based on the laminar Hartmann layer thickness, of approximately 380, valid also for laminarization and for a wide range of intensities of the magnetic field. The sensitivity of this result to the roughness characteristics of the walls along which the Hartmann layers develop confirms that these layers are related to the transition observed and provides more information on its stability properties.