Unsteady radiative stagnation point flow of MHD carreau nanofluid over expanding/contracting cylinder

The unsteady magnetohydrodynamic (MHD) stagnation point flow of Carreau nanofluid over an expanding/contracting cylinder in the presence of nonlinear thermal radiation is investigated numerically in this article. Recently devised model for nanofluid namely Buongiomo's model involving Brownian motion and thermophoresis is considered in the present problem. Additionally, zero nanoparticle mass flux condition at the boundary is considered. Mathematical problem is developed with the help of momentum, energy and nanoparticle concentration equations using suitable transformation variables. The numerical results for the transformed highly nonlinear ordinary differential equations are presented for both cases of stretching and shrinking cylinder in shear thinning as well as shear thickening fluids. For numerical computations, an effective numerical solver namely bvp4c package is used. Effects of involved controlling parameters on the velocity, temperature and nanoparticle concentration are examined. Numerical computations for the skin friction coefficient and Nusselt number are also executed. It is interesting to note that the temperature and nanoparticle concentration are higher in shrinking cylinder case when compared to stretching cylinder case. Additionally, the rate of heat transfer (Nusselt number) is a decreasing function of the unsteadiness, radiation and thermophoresis parameters in stretching and shrinking cylinder both for shear thickening and shear thinning fluids. (C) 2017 Elsevier Ltd. All rights reserved.