The thermal boundary layer of nanofluids over an unsteady stretching sheet with a convective surface boundary condition is
investigated. Two types of water based Newtonian nanofluids containing metallic or nonmetallic nanoparticles such as Copper (Cu) and
Alumina (Al2O3) are considered from a theoretical viewpoint and for a range of nanoparticle volume fractions. Using a similarity transformation
the governing time dependent nonlinear boundary layer equations for momentum and thermal energy are reduced to a set of
nonlinear ordinary differential equations. The resulting four-parameter problem is solved numerically using fourth order Runge-Kutta integration
scheme with shooting technique for some representative values of the unsteadiness parameter (A), the Prandtl number (Pr), local
Biot number (Bi) and solid volume fraction parameter (Φ). It is shown the both the shear stress and heat transfer rate at the sheet surface
are higher for Cu-water as compared to Al2O3-water. Besides, it is found that the heat transfer rate at the surface decreases with increasing
flow unsteadiness (A) and increases with increasing with increasing Bi and Φ. A comparison with a previous study available in
the literature has been done and we found an excellent agreement with them.
Keywords: Unsteady stretching sheet, nanofluids, convective heating, thermal boundary layer.
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