Thermal and bioconvective transport in Casson-based trimetallic nanofluid flow over a moving surface with gyrotactic microorganisms and thermophysical effects

This study presents a comprehensive analysis of steady, two-dimensional Casson fluid flow embedded with trimetallic nanoparticles copper (Cu), nickel (Ni), and zinc (Zn) suspended in engine oil over a stretching surface. The model incorporates the combined influences of thermal radiation, Joule heating, viscous dissipation, chemical reaction, and bioconvection due to gyrotactic microorganisms. Employing similarity transformations, the governing partial differential equations are reduced to a system of ordinary differential equations and solved numerically using a robust fourth-fifth order Runge–Kutta–Fehlberg method with a shooting technique. This study investigates the effects of key non-dimensional parameters, including the Casson parameter, magnetic field strength, porous medium permeability, mixed convection, buoyancy ratio, and Rayleigh number, on the velocity, temperature, solutal, and motile micro-organism distributions. Results show that increasing the Casson parameter and magnetic field intensity suppresses the velocity, while thermal and concentration profiles are significantly enhanced by thermal radiation and Eckert number. The influence of Schmidt numbers and bioconvection parameters on Sherwood and motile density numbers is also evaluated. The present results are found to be in good agreement with existing literature, confirming the validity of the proposed model. The outcomes of this work provide valuable insight into optimizing thermal and mass transport in nano-biofluid systems with implications in industrial coating, biomedical transport, and thermal energy harvesting applications.