International Journal of Physics and Mathematical Sciences ISSN: 2277-2111 (Online) An Open Access, Online International Journal Available at http://www.cibtech.org/jpms.htm 2014 Vol. 4 (4) October-December, pp. 56-70/Ahmed and Sinha Research Article © Copyright 2014 | Centre for Info Bio Technology (CIBTech) 56 MHD EFFECT ON UNSTEADY FLOW PAST AN ACCELERATED VERTICAL PLATE *Ahmed N. and Sinha S. Department of Mathematics, Gauhati University, Guwahati – 781014 *Author for Correspondence ABSTRACT An exact solution to the problem of a viscous incompressible electrically conducting fluid past an accelerated vertical plate with uniform mass diffusion is obtained. A uniform magnetic field is assumed to be applied normal to the plate directed into the fluid region. The Rosseland approximation is used to describe the radiative heat flux in the energy equation. The equations governing the flow are solved analytically by adopting Laplace transform technique in closed form. The profiles for the velocity, temperature, concentration fields, and skin-friction, Nusselt number and Sherwood number at the plate are demonstrated graphically for various values of the parameters involved in the problem and the results are physically interpreted. Keywords: MHD, Rotation, Thermal Radiation, Mass Transfer INTRODUCTION Many natural phenomena and technological problems are susceptible to MHD analysis. Geophysics encounters MHD characteristics in the interactions of conducting fluids and magnetic fields. Engineers employ MHD principle, in the design of heat exchangers pumps and flow meters, in space vehicle propulsion, thermal protection, braking, control and re-entry, in creating novel power generating systems etc. From technological point of view, MHD convection flow problems are also very significant in the fields of stellar and planetary magnetospheres, aeronautics, chemical engineering and electronics. Model studies of the above phenomena of MHD convection have been made by many. Some of them are Sanyal and Bhattacharya (1992), Ferraro and Plumpton (1966) and Cramer and Pai (1973). On the other hand, along with free convection currents, caused by the temperature difference, the flow is also affected by the difference in concentrations on material constitutions. Many investigators have studied the phenomena of MHD free convection and mass transfer flow of who the names of Acharya et al., (2000), Raptis and Kafousias (1982), Singh and Singh (2000) and Singh et al., (2007) are worth mentioning. Radiation is a process of heat transfer through electromagnetic waves. Radiative convective flows are encountered in countless industrial and environment process. Radiative heat and mass transfer play an important role in manufacturing industries for the design of reliable equipotent. If the temperature of the surrounding field is rather high, radiation effect plays an important role in space related technology. The effect of radiation on various convective flows under different conditions has been studied by many researchers including Hussain and Takhar (1996), Ahmed and Sarmah (2009), Rajesh and Varma (2010) and Ahmed et al., (2013). Investigation of problems on natural convective radiating flow of electrically conducting fluid past an infinite plate becomes very interesting and fruitful when a magnetic field is applied normal to the plate. Comprehensive literature on various aspects of free convective radiative MHD flows and its applications can be found in Sattar and Maleque (2000), Samad and Rahman (2006), Prasad et al., (2006), Takhar et al., (1996), Ahmed and Sarmah (2009) and Ahmed (2012). The effect of rotation on unsteady hydromagnetic natural convection flow of a viscous incompressible electrically conducting fluid past an impulsively moving vertical plate with ramped wall temperature has been investigated recently by Seth et al., (2011). The geophysical importance of the flows in rotating frame of reference has attracted the attention of a number of scholars. Model studies in this literature have been done by many. Some of them are Vidyanidhu and Nigam (1967) and Jana and Datta (1977). The effects of uniform transverse magnetic field with or without suction on different flow characteristics were investigated by Gupta (1972), Soundalgekar and Pop (1973) and Mazumdar et al., (1976).