## THERMAL SCIENCE

International Scientific Journal

### EFFECTS OF VARIABLE VISCOSITY AND THERMAL CONDUCTIVITY ON UNSTEADY MHD FLOW OF NON-NEWTONIAN FLUID OVER A STRETCHING POROUS SHEET

**ABSTRACT**

The unsteady flow and heat transfer in an incompressible laminar, electrically conducting and non-Newtonian fluid over a non-isothermal stretching sheet with the variation in the viscosity and thermal conductivity in a porous medium by the influence of an external transverse magnetic field have been obtained and studied numerically. By using similarity analysis the governing differential equations are transformed into a set of non-linear coupled ordinary differential equations which are solved numerically. Numerical results were presented for velocity and temperature profiles for different parameters of the problem as power law parameter, unsteadiness parameter, radiation parameter, magnetic field parameter, porous medium parameter, temperature buoyancy parameter, Prandtl parameter, modified Eckert parameter, Joule heating parameter , heat source/sink parameter and others. A comparison with previously published work has been carried out and the results are found to be in good agreement. Also the effects of the pertinent parameters on the skin friction and the rate of heat transfer are obtained and discussed numerically and illustrated graphically.

**KEYWORDS**

PAPER SUBMITTED: 2011-05-29

PAPER REVISED: 2012-01-17

PAPER ACCEPTED: 2012-02-08

**THERMAL SCIENCE** YEAR

**2013**, VOLUME

**17**, ISSUE

**Issue 4**, PAGES [1035 - 1047]

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