Numerical and statistical analysis of micropolar Carreau tri-hybrid nanofluid flow over a stretching cylinder with MHD and thermal radiation effects

This study investigates the flow of micropolar Carreau tri-hybrid nanofluid over a stretching cylinder, aiming to meet the increasing demand for improved heat transfer in biomedical and industrial applications. This work analyzes the unsteady thermal flow of a micropolar Carreau tri-hybrid nanofluid (CuO − MgO − TiO 2 in blood) over a stretching cylinder under the combined effects of magnetic fields (MHD), nonlinear thermal radiation, and viscous dissipation. The objective is to examine the impact of micropolar and non-Newtonian effects on velocity, temperature, entropy formation, and heat transfer, and to formulate predictive statistical models for engineering parameters. The governing boundary-layer equations are transformed via similarity variables and solved numerically using a Runge–Kutta–Fehlberg, Shooting method. Key findings demonstrate that increasing the radiation parameter ( R d ) from 1.0 to 3.0 improves the Nusselt number, while elevating the Weissenberg number ( W e ) from 1 to 5 raises near-wall velocity. Higher Brinkman numbers and magnetic field intensities accelerate entropy production, suggesting higher thermal irreversibility. Multiple linear regression yields a satisfactory prediction accuracy ( R 2 = 0 . 97 ) for Nusselt numbers and skin-friction coefficients supporting the statistical model. This work emphasises the value of tri-hybrid micropolar nanofluids in attaining regulated thermal performance, which is applicable in targeted medication administration, hyperthermia therapy, microelectronic cooling, and solar thermal systems. • Investigated the effects of MHD, heat radiation, and viscous dissipation on the unsteady micropolar Carreau tri-hybrid nanofluid flow ( C u O − M g O − T i O 2 ) in blood along a stretching cylinder. • Regression research revealed important factors affecting heat and flow behaviour after investigating entropy generation, Bejan number, and transport parameters.