Flow and heat transfer of an Oldroyd-B nanofluid thin film over an unsteady stretching sheet

The unsteady boundary layer flow and heat transfer of an incompressible Oldroyd-B nanofluid thin film due to a stretching sheet have been investigated analytically. Two different types of nanoparticles Cu and Ag are considered with poly vinyl alcohol (PVA)-water used as a base fluid. The velocity and temperature of the stretching sheet are assumed to vary both along the sheet and with time. The unsteady boundary layer governing equations are firstly established and then reduced to the coupled 4-order nonlinear ordinary differential equations by similarity transformation. The analytical solutions are obtained using the homotopy analysis method (HAM), and show good agreement compared with previous results. The influences of various relevant parameters such as unsteady parameter, volume fraction of Cu/Ag and Prandtl number on the flow field are elucidated through tables and graphs. (c) 2016 Elsevier B.V. All rights reserved.