Numerical investigation and regression analysis of EMHD tri-hybrid Sisko nanofluid flow over a stretching cylinder with nonlinear radiation and wall transpiration

Enhancing the thermal performance of electromagnetohydrodynamic Sisko fluid systems is relevant to advanced thermal-transport applications ranging from naval propulsion to nuclear-reactor cooling. This study investigates the mixed-convection flow and heat transfer of a nonlinear radiative tri-hybrid Sisko nanofluid over a stretching cylinder under electromagnetic forcing and wall suction/blowing. The study extends existing Sisko-flow analyses by considering electromagnetic forcing, nonlinear thermal radiation, wall transpiration, and tri-hybrid nanoparticle loading within the stretching-dominated and free-stream-dominated regimes. The governing equations are reduced through a local-similarity transformation and solved numerically using MATLAB bvp5c. The numerical results reveal a pronounced dependence of the momentum field on the velocity-ratio regime, whereas several thermal responses remain comparatively consistent across the two regimes. Increasing the mixed-convection and electric parameters enhances the velocity while reducing the temperature, whereas nonlinear radiation and the temperature ratio increase the thermal field. The Sisko material parameter and power-law index exhibit regime-dependent or spatially varying influences on the flow and thermal characteristics. Multiple linear regression with standardized predictors is further employed as a first-order surrogate for the skin-friction coefficient and Nusselt number. The power-law index exhibits the largest linear sensitivity of the Nusselt number, with regression coefficients of 0.390 in the stretching-dominated regime and 0.402 in the free-stream-dominated regime. In contrast, the Sisko material parameter shows the largest coefficient magnitude for the skin-friction response, with corresponding coefficients of -0.180 and 0.267. The results emphasize the dependence of momentum and heat-transfer behavior on Sisko rheology, wall transpiration, electromagnetic forcing, thermal radiation, and the relative wall-to-free-stream velocity.