Numerical Analysis of Unsteady Natural Convection Flow and Heat Transfer in the Existence of Lorentz Force in Suddenly E
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https://doi.org/10.1007/s11630-020-1190-9
Article ID: 1003-2169(2019)00-0000-00
Numerical Analysis of Unsteady Natural Convection Flow and Heat Transfer in the Existence of Lorentz Force in Suddenly Expanded Cavity Using OpenFOAM SINGH Ranjit J., GOHIL Trushar B.* Department of Mechanical Engineering, Visvesvaraya National Institute of Technology, Nagpur - 440010, India © Science Press, Institute of Engineering Thermophysics, CAS and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract: The present study reveals the significance of the magnetic field or Lorentz force on the unsteady natural convection flow and heat transfer in the suddenly expanded cavity. The Lorentz force based magnetohydrodynamics (MHD) solver using electric potential formulation coupled with the energy equation by the means of Boussinesq approximation is developed in the open-source CFD tool OpenFOAM. The unsteady flow is generated by the buoyancy force keeping the Rayleigh number (Ra) at 109, at the fixed Prandtl number (Pr) of 0.71. The effects of the magnetic field on the flow and heat transfer are explained for various orientations of magnetic field (Bx, B45, and By) in terms of Hartmann number (Ha=0, 50, 100, 300 and 500). The increase in the magnetic field increases the strength of the Lorentz force, which regulates the flow pattern and suppresses down the unsteady nature of flow and heat transfer into the steady-state. It is perceived that the average Nusselt number decreases as the intensity of Bx and B45 magnetic field increases. However, for By magnetic field the average Nusselt number increases up to Ha of 100 as compared to the non-MHD case (Ha=0). The distribution of Lorentz force in the domain plays a significant role in the governing of the fluid flow and heat transfer.
Keywords: OpenFOAM, Lorentz force, Boussinesq approximation, natural convection
1. Introduction The convection heat transfer is one of the three basic modes of the heat transfer process and it has the most important form of the fluid flow inside the cavity [1, 2], where the fluid motion is brought by the density variation as the outcome of temperature alteration. Natural convection can be further classified as internal flow or external flow being governed on the basis of the geometry or the flow pattern of the fluid. When the fluid is surrounded by the solid surfaces, it is defined by internal flow, and when the solid surface is covered by the flowing fluid, it is termed as external flow. It is observed that the
Received: May 13, 2019 Associate editor: TANG Guihua
two main forms of natural convection flow process have been studied: (1) when the temperature gradient available in the direction parallel to the acceleration due to gravity, it happens when the bottom surface is heated, and the top wall is kept cold. (2) The temperature gradient is allowed to flow in the direction normal to the gravity, in the case when vertical side-walls are maintained as isothermal. The buoyancy-driven free convection flow and heat transfer within the domain have
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