Unsteady axisymmetric flow of nanofluid on nonlinearly expanding surface with variable fluid properties

Abstract

The physical phenomena of nanofluid at high temperature motivate us to analyze problems with temperature-reliant fluid properties, like viscosity and thermal conductivity. Since in glass blowing, viscosity and thermal conductivity of the fluid may gets affected in such high temperature. This communication deals with the unsteady flow of nanofluid generated by nonlinear expansion of the surface. Temperature-dependent fluid viscosity and thermal conductivity are considered in the investigation of the problem. The flow of nanofluid is modeled using famous the Buongiorno's two-phase model, which includes the simultaneous effect of Brownian motion and thermophoresis diffusion. Appropriate transformations are adopted to obtain the ODEs from governing PDEs. Then MATLAB ‘bvp4c’ computation is used to solve the problem and to get a clear insight of the influences of various parameters. Graphical comparisons are made to check the accuracy of used numerical method. The study explores that heat transfer rate significantly enhances by the index of nonlinearity, variable viscosity and thermal conductivity parameters. Unsteadiness of the flow can be used as a controlling parameter to reduce the surface drag, heat and nano-mass transfer rate. Variable viscosity parameter leads to enhance the velocity near the surface and reducing the concentration of the nanoparticles. The thermal and concentration boundary layer thickens with thermal conductivity parameters. Nanofluid temperature and concentration of nanoparticles decay with nonlinear expanding index.

Keywords

• Axisymmetric flow
• Unsteady nanofluid
• Nonlinear expanding sheet
• Variable viscosity
• Variable thermal conductivity