<p>This study explores the unsteady MHD stagnant point flow of a Casson trihybrid nanofluid comprising gold, silver, and aluminum oxide nanoparticles suspended in the blood of a rotating sphere, with special emphasis on entropy generation analysis aimed at minimizing useful energy losses and enhancing thermal performance. The research incorporates the impacts of quadratic convection, ohmic heating, nonlinear thermal radiation, Darcy–Forchheimer drag, and viscous dissipation. To facilitate numerical analysis, the governing time-dependent nonlinear PDEs are reduced to ordinary differential equations via similarity transformations, which are subsequently tackled using a shooting approach integrated with the fourth-order Runge–Kutta method. The results are validated through comparison with established benchmark solutions, demonstrating excellent agreement and confirming the accuracy of the proposed model. A detailed parametric study examines the influence of physical parameters on velocity components in both streamwise and rotational directions, temperature profiles, entropy generation, the Bejan number, surface shear stress, and heat transfer rate. It is observed that increasing the unsteady parameter from 0.7 to 0.9 enhances the friction factor in the <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$x^{ * }$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mi>x</mi> <mrow /> <mrow> <mrow /> <mo>∗</mo> </mrow> </mmultiscripts> </math></EquationSource> </InlineEquation>-direction from 3.335 to 3.370 (approximately 1.05%), in the <InlineEquation ID="IEq2"> <EquationSource Format="TEX">$z^{ * }$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mi>z</mi> <mrow /> <mrow> <mrow /> <mo>∗</mo> </mrow> </mmultiscripts> </math></EquationSource> </InlineEquation>-direction from 1.308 to 1.361 (approximately 4.1%), and the Nusselt number from 2.97 to 3.72 (approximately 25%), indicating improved momentum and thermal boundary layer performance. Moreover, entropy generation increases with the Brinkman number, while the Bejan number decreases, reflecting greater heat irreversibility. Rotation cases notably improve heat transfer and change flow behavior compared to non-rotating conditions. These findings underscore their relevance in biomedical applications, such as hyperthermia-based cancer treatment, targeted drug delivery, and wound healing.</p>

Computational study on MHD stagnation-point flow of Casson trihybrid nanofluid of a rotating sphere under various thermal radiations

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发表日期：

2025年9月2日

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M. Keerthiga,
P. Bala Anki Reddy

摘要

This study explores the unsteady MHD stagnant point flow of a Casson trihybrid nanofluid comprising gold, silver, and aluminum oxide nanoparticles suspended in the blood of a rotating sphere, with special emphasis on entropy generation analysis aimed at minimizing useful energy losses and enhancing thermal performance. The research incorporates the impacts of quadratic convection, ohmic heating, nonlinear thermal radiation, Darcy–Forchheimer drag, and viscous dissipation. To facilitate numerical analysis, the governing time-dependent nonlinear PDEs are reduced to ordinary differential equations via similarity transformations, which are subsequently tackled using a shooting approach integrated with the fourth-order Runge–Kutta method. The results are validated through comparison with established benchmark solutions, demonstrating excellent agreement and confirming the accuracy of the proposed model. A detailed parametric study examines the influence of physical parameters on velocity components in both streamwise and rotational directions, temperature profiles, entropy generation, the Bejan number, surface shear stress, and heat transfer rate. It is observed that increasing the unsteady parameter from 0.7 to 0.9 enhances the friction factor in the $x^{ * }$ $x^{*}$ -direction from 3.335 to 3.370 (approximately 1.05%), in the $z^{ * }$ $z^{*}$ -direction from 1.308 to 1.361 (approximately 4.1%), and the Nusselt number from 2.97 to 3.72 (approximately 25%), indicating improved momentum and thermal boundary layer performance. Moreover, entropy generation increases with the Brinkman number, while the Bejan number decreases, reflecting greater heat irreversibility. Rotation cases notably improve heat transfer and change flow behavior compared to non-rotating conditions. These findings underscore their relevance in biomedical applications, such as hyperthermia-based cancer treatment, targeted drug delivery, and wound healing.