Hartmann number

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

Convective Poiseuille flow of Al2O3-EG nanofluid in a porous wavy channel with thermal radiation

Abstract: In current article, convective Poiseuille boundary layer flow of ethylene glycol (C2H6O2)-based nanofluid with suspended aluminum oxide (Al2O3) nanoparticles through a porous wavy channel has been examined. The impact of thermal radiation, Ohmic dissipation, electric field, and magnetic fields are also considered. The flow is due to constant pressure gradient in a wavy frame of reference. The governed momentum and thermal boundary layer equations is system of PDE’s, which are converted to system of ODE’s via suitable similarity transformations. The homotopy analysis method is applied to solve the governed flow problem. Convergence of series solutions is inspected through h-curves and residual errors norm, whereas the optimal value of convergence control parameter is obtained by means of genetic algorithm Nelder–Mead approach. The influence of numerous involving parameters like Hartmann number, Grashof number, Eckert number, electric parameter, radiation parameter, and porosity parameter on flow, heat transfer, skin friction coefficient and Nusselt number are illustrated through graphs and discussed briefly.

Natural convection in a rectangular enclosure in the presence of a magnetic field with uniform heat flux from the side walls

Abstract: A numerical study is presented for magnetohydrodynamic free convection of an electrically conducting fluid in a two-dimensional rectangular enclosure in which two side walls are maintained at uniform heat flux condition. The horizontal top and bottom walls are thermally insulated. A finite difference scheme comprising of modified ADI (Alternating Direction Implicit) method and SOR (Successive-Over-Relaxation) method is used to solve the governing equations. Computations are carried out over a wide range of Grashof number, Gr and Hartmann number, Ha for an enclosure of aspect ratio 1 and 2. The influences of these parameters on the flow pattern and the associated heat transfer characteristics are discussed. Numerical results show that with the application of an external magnetic field, the temperature and velocity fields are significantly modified. When the Grashof number is low and Hartmann number is high, the central streamlines are elongated and the isotherms are almost parallel representing a conduction state. For sufficiently large magnetic field strength the convection is suppressed for all values of Gr. The average Nusselt number decreases with an increase of Hartmann number and hence a magnetic field can be used as an effective mechanism to control the convection in an enclosure.

Simulation of three dimensional MHD natural convection using double MRT Lattice Boltzmann method

Abstract: In this study, a three-dimensional mesoscopic simulation of magneto hydrodynamics (MHD) natural convection in a cubic cavity has been studied by new means of the Lattice Boltzmann method with double Multi-Relaxation-Time (MRT) model. In order to solve the momentum and energy equations, two different populations with various lattices have been used. This paper has been conducted for specific values of the Grashof number ( Gr = 2 × 1 0 3 _ 2 × 1 0 5 ) and Hartmann number (Ha=0–100), while the Prandtl number is fixed at Pr = 0 . 73 . The results are presented in the form of average and local Nusselt number and contours of temperature and velocity at different planes of the cavity. It was found that the double MRT-LBM method is an appropriate approach to solve the studied case. The present results also show that the increase of the Hartmann number causes the heat transfer to drop considerably. Also, the effect of Hartmann number increases by enhancing the Grashof number, as the reduction of average Nusselt number is 12% for Gr = 2 × 1 0 3 and 71% for Gr = 2 × 1 0 5 when Hartmann number increases from 0 to 100. In contrast with Hartmann number, increasing of Grashof number raises heat transfer rate and the average Nusselt number increases by more than three times by enhancing the Grashof number from 2 × 1 0 3 to 2 × 1 0 5 .

Enhancement of Heat Transfer Rate by Application of a Static Magnetic Field During Natural Convection of Liquid Metal in a Cube

Abstract: Natural convection of liquid metal in a cubical enclosure under an external magnetic field was investigated by three-dimensional numerical analyses. The system parameters were Ra = 105 and 106 , Pr = 0.025, and Ha = 0–1000. One vertical wall of the cubical enclosure was heated, and the opposing vertical wall was cooled, both isothermally; the other four walls were thermally insulated. A uniform horizontal magnetic field was applied parallel to the heated and cooled walls. At Ra = 105 and Ha = 50, the average Nusselt number on the heated wall attained almost the maximum value and was greater than that at Ha = 0. The velocity vectors along the vertical walls, and those along the horizontal planes, were rectified in a two-dimensional way at Ha = 50 or over, and the average Nusselt number decreased gradually for higher values of the Hartmann number. Similar characteristics were obtained at Ra = 106 . The agreement with our earlier experiments was moderately good.