Effects of Variable Viscosity on Asymmetric Flow of Non-Newtonian Fluid Driven Through an Expanding/Contracting Channel Containing Porous Walls

Flow in porous channel or pipe has attained significant attention in biophysics, especially when the walls are contracting or expanding. The purpose of this work is to explore the effects of variable viscosity on the asymmetric laminar flow of Casson fluid (CF) with thermal radiation in an expanding/contracting channel having porous walls. The flow equations, by using appropriate transformations, are reduced to ordinary differential equations (ODEs). The method of homotopy analysis (HAM) is used to obtain the expressions for the velocity field along with the temperature profile. Graphs are portrayed for different parametric values and analyzed in detail for the consequent dynamic attributes, especially the viscosity-dependent parameter, CF parameter, and the expansion ratio. CF parameter escalates the velocity of the fluid near the lower wall, but after mid-way, it starts decreasing. The fluid velocity due to temperature-dependent (TD) viscosity parameter is more noteworthy for Newtonian fluid (NF) relative to non-Newtonian (NN) fluid. As anticipated, the radiation parameter causes the fluid to heat up.