Carbon nanotubes effects in the stagnation point flow towards a nonlinear stretching sheet with variable thickness

The aim of present communication is to investigate the stagnation point flow of viscous nanofluid towards a nonlinear stretching surface with variable thickness. Analysis for both single-wall carbon nanotubes (SWNTs) and multi-wall carbon nanotubes (MWNTs) is presented and compared. Water and kerosene oil are employed as the ordinary (or base) fluids. Mathematical modeling and analysis are attended in the presence of porous medium, melting heat transfer and homogeneous and heterogeneous reactions. Diffusion coefficients for autocatalyst and reactant are treated similar. Series solutions of the governing nonlinear modeled problems have been constructed by using optimal homotopy analysis method (OHAM). This method is very efficient for development of series solutions of highly nonlinear differential equations. Computations for residual errors are prepared. Comparison of present study with the previous published work is also made. The velocity, temperature, concentration, skin friction coefficient and Nusselt number are discussed for different influential variables entering into the problems statements. The flow decreases for higher values of variable thickness parameter when m < 1 and it enhances when m > 1. Higher velocity profile is observed for volume fraction parameter in case of kerosene oil carbon nanotubes when compared with the water carbon nanotubes. The skin friction can be reduced by increasing ratio parameter and it advances by increasing volume fraction parameter. It is observed that MWCNTs has maximum heat transfer and minimum thermal resistance due to low density of MWCNTs when compared with SWNTs for water. The flow accelerates in case of MWCNTs than SWNTs for both base fluids namely water and kerosene oil. Comparison for the results of SWNTs and MWNTs is highlighted. Homogeneous reaction parameter corresponds to decrease in the concentration distribution and opposite behavior is observed for heterogeneous reaction parameter. Such consideration may play a vital role in industrial process as a cooling agent. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.