Significance of Yamada–Ota and Xue models in shear flow analysis of hybrid nanofluids within converging boundary layers of varying strengths

This study investigates the impact of thermal radiation on the shear flow of two immiscible water-based hybrid nanofluids containing carbon nanotubes, confined within converging boundary layers of unequal strengths. The analysis focuses on comparing two widely used thermal conductivity models, namely, the Yamada–Ota and Xue models for hybrid nanofluids composed of single-walled (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). By applying appropriate similarity transformations, the governing partial differential equations are reduced to a set of nonlinear ordinary differential equations, which are solved numerically using MATLAB's bvp4c solver. The effects of key parameters, including viscosity ratio, thermal conductivity ratio, radiation, and Schmidt number on velocity, temperature, and concentration fields, are examined in detail. Results demonstrate that the Xue model predicts a steeper temperature gradient compared to the Yamada–Ota model, and that increasing the Schmidt number reduces mass transfer in both fluid layers. The comparative analysis provides valuable insights for optimizing thermal and mass transport in stratified flow systems, with potential applications in microchannel heat exchangers, layered cooling devices, and energy systems.