Hartmann number

About: Hartmann number is a research topic. Over the lifetime, 2593 publications have been published within this topic receiving 61342 citations.

Heat transfer augmentation of magnetohydrodynamics natural convection in l-shaped cavities utilizing nanofluids

Abstract: A numerical study of natural convection heat transfer through an alumina-water nanofluid inside L-shaped cavities in the presence of an external magnetic field is performed. The study has been carried out for a wide range of important parame­ters such as Rayleigh number, Hartmann number, aspect ratio of the cavity and solid volume fraction of the nanofluid. The influence of the nanoparticle, buoyancy force and the magnetic field on the flow and temperature fields have been plotted and discussed. The results show that after a critical Rayleigh number depending on the aspect ratio, the heat transfer in the cavity rises abruptly due to some significant changes in flow field. It is also found that the heat transfer enhances in the presence of the nanoparticles and increases with solid volume fraction of the nanofluid. In addition, the performance of the nanofluid utilization is more effective at high Ray­leigh numbers. The influence of the magnetic field has been also studied and de­duced that it has a remarkable effect on the heat transfer and flow field in the cavity that as the Hartmann number increases the overall Nusselt number is significantly decreased specially at high Rayleigh numbers.

Unsteady MHD Couette Flows in an Annuli: The Riemann-Sum Approximation Approach

Abstract: The unsteady MHD Couette flow of a viscous incompressible electrically conducting fluid between two concentric horizontal cylinders of infinite length have been analysed when the outer cylinder has been set into uniform accelerated motion. A unified closed form expressions are derived corresponding to the cases of the magnetic field fixed relative to the fluid or to the accelerated outer cylinder. The well known Laplace transform technique is applied to solve the time-dependent governing equations, while the method of Riemann-sum approximation is employed to invert the Laplace domain to the time domain in order to obtain the velocity and the skin friction. The variations of the velocity and the skin friction with respect to the Hartmann number and time have been discussed.

Application of Differential Transformation Method for Nanofluid Flow in a Semi-Permeable Channel Considering Magnetic Field Effect

Abstract: In this study, we propose a reliable algorithm to develop an analytical solution for the problem of laminar steady magnetohydrodymanics (MHD) nanofluid flow in a semi-permeable channel using the differential transformation method (DTM). The working fluid is water with copper nanoparticles. The effects of Hartmann number and Reynolds number on velocity profiles have been also considered for various numerical cases. The effective thermal conductivity and viscosity of nanofluid are calculated by the Maxwell and Brinkman models, respectively. A close agreement between the obtained solution and some well-known results has been established.

Mesoscopic analysis of MHD double diffusive natural convection and entropy generation in an enclosure filled with liquid metal

Abstract: In this numerical study, the entropy generation in double-diffusive natural convection in a square enclosure with the presence of adiabatic rectangular block at the center of the enclosure is examined. The uniform magnetic field is applied horizontally to the enclosure. The Lattice–Boltzmann approach is carried out to solve the governing equations. The linear increment of heat is applied to the left wall of the cavity. Both horizontal walls are an adiabatic condition, and the right wall is considered to be at cold temperature. The analysis is carried out for different range of operating parameters such as Rayleigh number (103 ≤ Ra ≤ 105), Lewis number (2 ≤ Le ≤ 10), buoyancy ratio (−2 ≤ N ≤ 2), Hartmann number (0 ≤ Ha ≤ 50) for the liquid metal sodium-potassium (NaK) alloy with Prandtl number (Pr) 0.054. Increasing Rayleigh number causes the entropy generation to expand, and increasing Ha decreases the total entropy generation for all Ra values. For the present problem, the critical N value is found to be −1.5. The rise of Le leads to the augmentation of irreversibility in the enclosure. The decrement of SF when compared with Ha = 0 and 50 is 97%, 91.5% and 75.64% for Ra = 103, 104, and 105, respectively.