Effects of Hall current and heat transfer on flow due to a pull of eccentric rotating disks S. Asghar a , Muhammad R. Mohyuddin b, * , T. Hayat b a COMSATS, Institute of Information Technology, Abbottabad 22010, Pakistan b Department of Mathematics, Quaid-i-Azam University 45320, Islamabad 44000, Pakistan Received 18 June 2003; received in revised form 6 August 2004 Available online 11 November 2004 Abstract The influence of Hall current and heat transfer on the magnetohydrodynamic (MHD) flow of an Oldroyd-B fluid is investigated. The fluid is between two infinite disks rotating about non-coaxial axes normal to the disks in the presence of a uniform transverse magnetic field. The flow is due to a constant velocities of eccentric rotating disks. Exact solu- tions are derived for the velocity, force and torque exerted by the fluid on one of the disk and temperature distribution. Ó 2004 Elsevier Ltd. All rights reserved. 1. Introduction In recent years the theoretical study of MHD channel flows has been a subject of great interest due to its wide- spread applications in designing cooling systems with liquid metals, petroleum industry, purification of crude oil, polymer technology, centrifugal separation of matter from fluid, MHD generators, pumps, accelerators and flow meters. Various workers [1–6] have analyzed the interesting problems in this direction. More recently, Ersoy [7] discussed the flow due to a pull with constant velocities of eccentric rotating disks with the same angu- lar velocity. In another paper Ersoy [8] examined the MHD flow of a non-Newtonian fluid between eccentric rotating disks. Unfortunately, the results of the above investigations cannot be applied to the flow of ionized gases. In an ion- ized gas where the density is low and/or the magnetic field is very strong, the conductivity normal to the mag- netic field is reduced due to the free spiraling of electrons and ions about the magnetic lines of force before suffer- ing collisions; also, a current is induced in a direction normal to both the electric and magnetic fields. The phe- nomena, well known in the literature, is called the Hall effect. The study of magnetohydrodynamic flows with Hall currents has important engineering applications in problems of magnetohydrodynamic generators and of Hall accelerators as well as in flight magnetohydrody- namics. Sato [9], Sherman and Sutton [10], Hossain [11], Hossain and Mohammad [12], Hossain and Rashid [13], Pop [14], Raptis and Ram [15] and Ram [16] stud- ied the Hall effects. In this paper, we generalize the work of Ersoy [7,8] and investigate the effects of Hall current and heat trans- fer on the steady flow of an electrically conducting, Old- royd-B and incompressible fluid. The fluid is between two electrically insulating disks maintained at two con- stant but different temperatures. The flow is due to a pull with constant velocities of eccentric rotating infinite disks and an external uniform magnetic field is applied 0017-9310/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijheatmasstransfer.2004.08.023 * Corresponding author. Tel.: +92 51 2275 341. E-mail address: m_raheel@yahoo.com (M.R. Mohyuddin). International Journal of Heat and Mass Transfer 48 (2005) 599–607 www.elsevier.com/locate/ijhmt