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<p>The present study provides a detailed numerical investigation of steady, mixed-convective magnetohydrodynamic (MHD) Casson nanofluid flow through a vertical cylindrical annulus embedded in a non-Darcy porous medium. The formulation incorporates the Cattaneo–Christov double-diffusion model, replacing classical Fourier and Fick laws to account for finite thermal and solutal relaxation effects. Additional physical mechanisms include Darcy–Forchheimer inertial drag, Lorentz force, Joule heating, temperature-dependent viscosity and electrical conductivity, Arrhenius activation energy, and non-uniform internal heat generation/absorption. Three base fluids namely ethylene glycol (EG), engine oil (EO), and kerosene (Kr) containing Fe₃O₄ nanoparticles are systematically analyzed. The governing partial differential equations are transformed into a system of nonlinear, coupled ordinary differential equations using the fully developed flow assumption with imposed axial gradients in temperature and concentration. The resulting boundary value problem is solved using a one-dimensional Galerkin finite element method (GFEM) with quadratic Lagrange interpolation and Newton–Raphson linearization. The results reveal that increasing the thermal Deborah number (De₁) from 0.1 to 0.3 enhances the wall Nusselt number by approximately 15–18%, highlighting the importance of non-Fourier heat transport. Among the nanofluids, Fe₃O₄–EG exhibits superior heat transfer performance, with Nusselt numbers exceeding those of Fe₃O₄–EO and Fe₃O₄–Kr by 8.7–11.4%, respectively. Conversely, Fe₃O₄–Kr achieves the highest Sherwood number, surpassing the EG-based nanofluid by about 3.6% due to lower mass diffusivity. The wall skin-friction coefficient decreases by nearly 9% as the Casson parameter (β) increases from 0.2 to 0.6. Furthermore, increasing the magnetic parameter (M) from 0.5 to 1.0 reduces axial velocity by approximately 12% while elevating temperature due to Ohmic dissipation. The numerical results show excellent agreement with benchmark data, confirming the accuracy and robustness of the proposed model. The present findings may provide useful theoretical guidance for understanding heat and mass transfer behaviour in annular configurations relevant to heat-exchanger and reactor-cooling applications.</p>

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Synergistic interplay of thermal relaxation, variable thermophysical properties, and non-darcy transport phenomena in magnetohydrodynamic Casson nanofluid flow through a cylindrical annulus

  • 期刊论文

  • 发表日期：

    2026年6月24日

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  • Suguna H.G.,
  • P. Chandrakala

摘要

The present study provides a detailed numerical investigation of steady, mixed-convective magnetohydrodynamic (MHD) Casson nanofluid flow through a vertical cylindrical annulus embedded in a non-Darcy porous medium. The formulation incorporates the Cattaneo–Christov double-diffusion model, replacing classical Fourier and Fick laws to account for finite thermal and solutal relaxation effects. Additional physical mechanisms include Darcy–Forchheimer inertial drag, Lorentz force, Joule heating, temperature-dependent viscosity and electrical conductivity, Arrhenius activation energy, and non-uniform internal heat generation/absorption. Three base fluids namely ethylene glycol (EG), engine oil (EO), and kerosene (Kr) containing Fe₃O₄ nanoparticles are systematically analyzed. The governing partial differential equations are transformed into a system of nonlinear, coupled ordinary differential equations using the fully developed flow assumption with imposed axial gradients in temperature and concentration. The resulting boundary value problem is solved using a one-dimensional Galerkin finite element method (GFEM) with quadratic Lagrange interpolation and Newton–Raphson linearization. The results reveal that increasing the thermal Deborah number (De₁) from 0.1 to 0.3 enhances the wall Nusselt number by approximately 15–18%, highlighting the importance of non-Fourier heat transport. Among the nanofluids, Fe₃O₄–EG exhibits superior heat transfer performance, with Nusselt numbers exceeding those of Fe₃O₄–EO and Fe₃O₄–Kr by 8.7–11.4%, respectively. Conversely, Fe₃O₄–Kr achieves the highest Sherwood number, surpassing the EG-based nanofluid by about 3.6% due to lower mass diffusivity. The wall skin-friction coefficient decreases by nearly 9% as the Casson parameter (β) increases from 0.2 to 0.6. Furthermore, increasing the magnetic parameter (M) from 0.5 to 1.0 reduces axial velocity by approximately 12% while elevating temperature due to Ohmic dissipation. The numerical results show excellent agreement with benchmark data, confirming the accuracy and robustness of the proposed model. The present findings may provide useful theoretical guidance for understanding heat and mass transfer behaviour in annular configurations relevant to heat-exchanger and reactor-cooling applications.