Purpose The purpose of this paper is to focus on the application of Chebyshev spectral collocation methodology with Gauss Lobatto grid points to micropolar fluid over a stretching or shrinking surface. Radiation, thermophoresis and nanoparticle Brownian motion are considered. The results have attainable scientific and technological applications in systems involving stretchable materials. Design/methodology/approach The model equations governing the flow are transformed into non-linear ordinary differential equations which are then reworked into linear form using the Newton-based quasilinearization method (SQLM). Spectral collocation is then used to solve the resulting linearised system of equations. Findings The validity of the model is established using error analysis. The velocity, temperature, micro-rotation, skin friction and couple stress parameters are conferred diagrammatically and analysed in detail. Originality/value The study obtains numerical explanations for rapidly convergent solutions using the spectral quasilinearization method. Convergence of the numerical solutions was monitored using the residual error analysis. The influence of radiation, heat and mass parameters on the flow are depicted graphically and analysed. The study is an extension on the work by Zheng et al. (2012) and therefore the novelty is that the authors tend to take into account nanoparticles, Brownian motion and thermophoresis in the flow of a micropolar fluid.

The study considers gold-water nanofluid flow past a porous rotating disk while accounting for prescribed heat flux and suction at the boundary layer of the disk. The physical parameters of the nanoparticle volume fraction, magnetic parameter and entropy generation are investigated and presented in this paper. The numerically solved nonlinear equations by the spectral quasilinearization technique. The main findings are presented in graphical form and discussed for variations of the flow parameters. The findings indicate that increased nanoparticle volume concentration fall in velocity but a overshoot in temperature, while enhancing the magnetic parameter is associated with reduced velocity distribution and increased skin friction. Among other findings, the results also show that increasing the Brinkman number leads to increased entropy generation but reduced Bejan number, while the Reynolds number increasing in the generation of elevated levels of entropy production. The reliability, error analysis and accuracy are checked through convergence of the method. The accuracy is further tested through a comparison of results for limiting cases with those in the literature. The findings of this study have significant applications in engineering, science and technology.