HEAT TRANSFER FOR TWO TYPES OF VISCOELASTIC FLUID OVER AN EXPONENTIALLY STRETCHING SHEET WITH VARIABLE THERMAL CONDUCTIVITY AND RADIATION IN POROUS MEDIUM

An analysis has been carried out to study the boundary layer flow and heat transfer characteristics of second order fluid and second grade fluid with variable thermal conductivity and radiation over an exponentially stretching sheet in porous medium. The basic boundary layer equations governing the flow and heat transfer in prescribed surface temperature and prescribed heat flux cases are in the form of partial differential equations. These equations are converted to non-linear ordinary differential equations using similarity transformations. Numerical solutions of the resulting boundary value problem are solved by using the fourth order Runge-Kutta method with shooting technique for various values of the physical parameters. The effect of variable thermal conductivity, porosity, Prandtl number, radiation parameter, and viscoelastic parameters on velocity and temperature profiles (in prescribed surface temperature and prescribed heat flux cases) are analyzed and discussed through graphs. Numerical values of wall temperature gradient in prescribed surface temperature case and wall temperature in prescribed heat flux case are obtained and tabulated for various values of the governing parameters. In this study Prandtl number also treated as variable inside the boundary layer because it depends on thermal conductivity. The results are also verified by using finite difference method.