Thermal Radiation Effect on Mixed Convective Casson Fluid Flow over a Porous Stretching Sheet with Variable Fluid Properties

The effects of the variation of radiation and fluid characteristics on the flow, heat transfer, and mass transfer of a non-Newtonian Casson fluid at a vertical permeable stretched sheet are explored. We focus on the assumption that the behavior of the particles in the fluid is sensitive to both temperature and species diffusion, and we investigate their combined impacts. By using an appropriate similarity transformation, the governing nonlinear partial differential equations are converted into a system of highly nonlinear coupled ordinary differential equations. We apply a semi-analytical method for different physical parameters to solve the resultant system with proper boundary conditions. By employing the optimal homotopy analysis method (OHAM), which allows for the regulation and modification of the convergence zone, we are able to derive analytical solutions for the dimensionless velocity, temperature, and concentration fields. Our findings demonstrate that, compared to the homotopy analysis approach (HAM) proposed by Liao [1], OHAM solutions are more accurate approximations of the precise solutions for large values of the independent variable. By plotting the residual errors and comparing them to results in the literature, we can ensure that our analytical solution is correct for certain edge situations. Our method was validated by the comparison, which showed a high degree of agreement. Due to the presence of permeability parameter the velocity profile decreases, whereas the temperature and concentration profile increases. Since radiation parameter is directly connected to the free stream temperature, increasing values of radiation parameter, the thermal boundary layer thickness gets enhanced.