Ashwini Bhat

This study investigates magnetohydrodynamic (MHD) flow and heat transfer in a semi-infinite expanding or contracting porous pipe under local thermal non-equilibrium (LTNE) conditions with wall suction and injection. The governing momentum and energy equations for the fluid and solid phases are transformed into nonlinear ordinary differential equations using similarity transformations and then solved using the optimal homotopy analysis method (OHAM). The impacts of wall expansion/contraction, permeation Reynolds number, Hartmann number, inverse Darcy number, Prandtl number, heat capacity ratio, interphase heat transfer parameter, and porosity-scaled conductivity parameter on the flow and heat transfer characteristics are examined. The results indicate that wall expansion and suction increase the normalised centreline axial velocity and modify the magnitude of the radial velocity within the pipe, while the coupled effects of porous-medium resistance and magnetic field suppress the fluid flow. The LTNE framework reveals distinct thermal responses of the fluid and solid phases, demonstrating that the local thermal equilibrium assumption may lead to inaccurate heat transfer predictions in porous media where interphase thermal interactions are finite. The hydrodynamic results show close agreement with previously reported solutions under the corresponding limiting conditions, thereby validating the accuracy of the present flow solution.

This study investigates the linear stability of magnetohydrodynamic (MHD) flow in a porous channel with Navier-slip boundary conditions and lower-wall surface roughness to clarify the combined effects of these mechanisms on flow transition. A modified Orr–Sommerfeld eigenvalue model incorporating the Reynolds number, Hartmann number, Darcy number, slip parameter, and roughness wavenumber is formulated and solved using the Chebyshev spectral collocation method. The results demonstrate that surface roughness has a negligible effect on the base-flow profile, while increasing the roughness wavenumber enhances disturbance attenuation and promotes flow stability. Wall slip increases the base-flow velocity and further suppresses disturbance growth. The Hartmann number provides strong magnetic damping, significantly enhancing flow stability. In contrast, increasing the Darcy number reduces porous-medium resistance and promotes instability, leading to a transition from stable to unstable behaviour within the investigated parameter range. The numerical results closely match established benchmark solutions, demonstrating the accuracy and robustness of the proposed approach. These findings provide new insights into the coupled influence of wall slip, surface roughness, porous permeability, and magnetic effects on hydrodynamic stability, with potential applications in MHD transport systems, porous channels, microfluidic devices, and advanced thermal management technologies.

1. The stagnation point, which refers to the flow field where the fluid velocity becomes zero. The study of viscous, incompressible fluid flow through a permeable plate or sheet is essential to flu...

Magnetorheological (MR) fluids are widely used in adaptive damping systems, smart lubrication devices, microfluidic control systems, and magnetically regulated valves because their flow behaviour can be rapidly controlled using external magnetic fields. Accurate prediction of MR fluid transport in porous channels is therefore important for improving the efficiency and stability of such smart engineering systems. However, limited studies have simultaneously incorporated magnetic-field-dependent rheology, porous resistance, and wall slip effects within a unified mathematical framework. The present study aims to develop a mathematical model for steady incompressible MR fluid flow through a porous channel formed by parallel plates under the influence of a transverse magnetic field. The formulation incorporates a power-law-based equivalent viscosity model together with Darcy–Forchheimer porous resistance and velocity-slip boundary conditions. The governing nonlinear equations are transformed into dimensionless form using similarity transformations and solved numerically using the MATLAB boundary-value solver bvp4c . Additionally, numerical accuracy is validated using a fourth-order Runge–Kutta (RK4) shooting method. The results demonstrate that increasing the Hartmann number from 1 to 15 reduces the axial velocity from 1.27337 to 1.06740 due to enhanced Lorentz forces opposing the flow. Similarly, increasing the Forchheimer parameter from 0 to 3 decreases the velocity near the channel walls from 1.54182 to 1.31603 because of stronger inertial resistance within the porous medium. Furthermore, increasing the rheological parameter from 2 to 2.8 raises the shear stress from 3.13838 to 3.62397, indicating enhanced non-Newtonian resistance, whereas increasing the slip parameter from 0 to 0.5 reduces the velocity from 1.19049 to 1.04308 by weakening wall-fluid interaction. The proposed model successfully captures the coupled influence of magnetic damping, porous resistance, rheological effects, and wall slip behaviour, providing useful theoretical insight for the design and optimisation of MR-based smart flow-control and adaptive engineering systems.

The present study investigates heat transfer characteristics in the thermally developing region of a porous tube under the local thermal nonequilibrium (LTNE) model. The influence of magnetohydrodynamic (MHD) flow on an electrically conducting fluid flowing through a porous medium under a transverse magnetic field is examined. Under the LTNE framework, two separate energy equations are employed to describe the temperature fields of the fluid and solid phases. The coupled governing equations are solved numerically using the Keller-box method. The results indicate that increasing the interphase heat transfer parameter strengthens thermal coupling between the fluid and solid phases, thereby reducing temperature differences and promoting local thermal equilibrium. In contrast, an increase in the Prandtl number reduces thermal diffusion, leading to larger temperature gradients and greater disparity between the two phases. Furthermore, the magnetic field suppresses both the velocity and temperature distributions through the Lorentz force. An increase in permeability reduces the velocity profiles due to the combined effects of the MHD and Prandtl numbers while increasing the temperature profiles. Increasing the interphase heat transfer rate drives the system from the LTNE to the LTE phase. The study confirms that LTNE effects play a significant role in thermal transfer processes in porous media and are relevant for various industrial heat transfer applications.

This study examines the linear stability of two-dimensional incompressible viscous flow through a parallel channel embedded in a porous medium under the influence of a transverse magnetic field and various slip boundary conditions. Employing the Brinkman model, the analysis integrates Navier-slip boundary formulations, including general, symmetric, and asymmetric configurations, to capture realistic surface-fluid interactions relevant to modern sustainable technologies. The modified Orr-Sommerfeld equation is solved using the Chebyshev spectral collocation method to determine velocity distributions, eigenvalues, and critical flow parameters with high numerical precision. The findings reveal that wall slip, particularly under symmetric conditions, tends to destabilise the flow by reducing wall shear stress, whereas porous resistance and asymmetric slip enhance hydrodynamic stability. An approximate 20-30% decrease in wall shear stress is related to the effect of increasing wall slope. However, the presence of a transverse magnetic field partially reduces this decrease, resulting in a 10-15% increase in wall shear stress due to magnetic damping. The role of magnetic influence and porous drag is systematically explored, offering valuable insights into optimising flow control for efficient resource utilisation, energy conservation, and environmentally responsive fluid systems. Overall, this work advances sustainable and resilient design in magnetohydrodynamic (MHD) energy systems, microfluidic devices, and porous transport technologies. Maintaining flow stability supports cleaner industrial operations and the development of energy-efficient technologies.

This research contributes to the field of materials engineering through an analysis of the wear performance of both glass fiber-reinforced epoxy composites (GFEC) and bamboo fiber-reinforced epoxy composites (BFEC). This study aims to assess the wear performance, defined by mass loss, of the composites under various factors: load, speed, time, nanoclay content, and composite type. Specimens are subjected to wear tests by a pin-on-disc tribometer. Composite wear performance is studied through Response Surface Methodology (RSM) and Artificial Neural Networks (ANN) as predictive models. Experimental runs are planned based on the Box–Behnken design of RSM to present a regression model that is then checked with an ANOVA analysis; afterwards, training and testing are performed using an ANN model to improve predictive accuracy. As per the results, GFEC exhibits lower mass loss compared to BFEC. For both of the composites, the mass loss is drastically reduced by the addition of nanoclay. The addition of nanoclay has more pronounced effects on BFECs than on GFECs. ANN predictions are found to be better in agreement with the experimental values compared to those derived from the RSM model. Scanning Electron Microscopy (SEM) analysis provides insight into wear mechanisms. This study demonstrates the effectiveness of a statistical and machine learning approach in optimizing wear performance in composite materials.