MHD bioconvective radiative flow of chemically reactive Casson nanofluid from a vertical surface with variable transport properties

In this paper, we analyse magnetohydrodynamic bioconvective flow of Casson nanofluid comprising gyrotactic microorganisms from a vertical surface with variable thermo-physical features, nonlinear radiation, chemical reaction, Hall and ion-slip currents. The Casson fluid model incorporates zero nanoparticle mass flux at the boundary along with aspects of Brownian motion and thermophoresis to improve the motion of nanoparticles. The inclusion of motile microorganisms is considered to be beneficial for the stability of the nanoparticles. The model equations are first reduced into dimensionless form and then solved numerically using overlapping multi-domain bivariate spectral quasilinearisation method. Numerical analysis of the residual error and convergence properties of the method are discussed. For validation, our numerical results were compared with those available in the literature, and an excellent agreement was found. The impact of significant parameters on the flow fields, skin friction coefficients, heat, mass and motile microorganism transfer rates are analysed. We found that the flow fields improve due to enhancement of variable thermal conductivity, whereas retard with increment in variable viscosity and Casson fluid parameter. The inclusion of variable thermal conductivity and nonlinear radiative heat flux augments the fluid temperature, heat and mass transfer rates. An increment in variable fluid viscosity and Casson fluid parameter enhances heat and motile microorganism transfer rates, whereas diminishes the mass transfer rate. The reported observations find applications in enrobing processes for electric-conductive nano-materials, can be used in aerospace, smart coating transport situation, polymer processing and other industries. This type of flow can efficiently be utilised in solar energy system, enhancement of extrusion systems, and improvement of heat transfer devices as well as microbial fuel cells.