Hartmann number

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

The effects of buoyancy force on mixed convection heat transfer of MHD nanofluid flow and entropy generation in an inclined duct with separation considering Brownian motion effects

Abstract: In this paper, an attempt is made to study the buoyancy force influences on the MHD mixed convection nanofluid flow and entropy generation over an inclined step in an inclined duct. This inclined step leads to the flow separation in duct and affects the hydrodynamic and thermal behaviors. Influences of Brownian motion on the effective viscosity and thermal conductivity of Cu-water nanofluid are considered. The second law of thermodynamics is used to calculate the entropy generation number that is an applied criterion to compute the flow irreversibility. The interaction effects of Grashof number $$ \left( {0 \le Gr \le 10,000} \right) $$, duct inclination angle $$ \left( {0^\circ \le \beta \le 90^\circ } \right) $$, Hartmann number $$ \left( {0 \le Ha \le 60} \right) $$ and concentration of $$ Cu $$ nanoparticles $$ \left( {0 \le \phi \le 0.06} \right) $$ on the flow pattern, heat transfer rates and the amount of flow irreversibility are studied with all details. The results show that the Hartmann number has a large influence on the trends of the fiction coefficient, Nusselt number and entropy generation number along the bottom wall. Also, the highest values of average friction coefficient and average Nusselt number occur in the absence of magnetic field and for the vertical duct with highest values of $$ Gr $$ and $$ \phi $$. In addition, an increase in the amounts of flow irreversibility is registered by enhancing the buoyancy force, magnetic field strength and nanoparticles concentration.

Rayleigh Bénard instability in a vertical cylinder with a vertical magnetic field

Abstract: This paper presents two linear stability analyses for an electrically conducting liquid contained in a vertical cylinder with a thermally insulated vertical wall and with isothermal top and bottom walls. There is a steady uniform vertical magnetic field. The first linear stability analysis involves a hybrid approach which combines an analytical solution for the Hartmann layers adjacent to the top and bottom walls with a numerical solution for the rest of the liquid domain. The second linear stability analysis involves an asymptotic solution for large values of the Hartmann number. Numerically accurate predictions of the critical Rayleigh number can be obtained for Hartmann numbers from zero to infinity with the two solutions presented here and a previous numerical solution which gives accurate results for small values of the Hartmann number.

Numerical investigation of nanofluid melting heat transfer between two pipes

Abstract: CuO-water nanofluid melting heat transfer between two circular cylinders is studied in existence of horizontal magnetic field. Effect of various shapes of nanoparticles on nanofluid properties is considered. The KKL model is utilized for estimating viscosity of nanofluid. Runge-Kutta integration scheme is selected for solving ODEs. Numerical procedures are examined for various active parameters namely shapes of nanoparticle, melting parameter (δ), Hartmann number (Ha), Eckert number (Ec) and Reynolds number (Re). Results show that temperature gradient increases with increase in Hartmann number but it decreases with increase in melting parameter. Velocity reduces with rise of Lorentz forces and melting parameter but it increases with increase in Reynolds number.

Heat and mass transfer in a vertical double passage channel filled with electrically conducting fluid

Abstract: This paper investigates the influence of first order chemical reaction in a vertical double passage channel in the presence of applied electric field. The wall and ambient medium are maintained at constant but different temperatures and concentrations and the heat and mass transfer occur from the wall to the medium. The channel is divided into two passages by means of a thin perfectly conducting baffle. The coupled non-linear ordinary differential equations are solved analytically by using regular perturbation method (PM) valid for small values of Brinkman number. To understand the flow structure for large values of Brinkman number the governing equations are also solved by differential transform method (DTM) which is a semi-analytical method. The effects of thermal Grashof number ( Gr T = 1 , 5 , 10 , 15 ), mass Grashof number ( Gr C = 1 , 5 , 10 , 15 ), Brinkman number ( Br = 0 , 0.1 , 0.5 , 1 ), first order chemical reaction parameter ( α = 0.1 , 0.5 , 1 , 1.5 ), Hartmann number ( M = 4 , 6 , 8 , 10 ) and electrical field load parameter ( E = − 2 , − 1 , 0 , 1 , 2 ) on the velocity, temperature and concentration profiles, volumetric flow rate, total heat rate, skin friction and Nusselt number are analyzed. It was found that the thermal Grashof number, mass Grashof number and Brinkman number enhances the flow whereas the Hartmann number and chemical reaction parameter suppresses the flow ​field. Also the obtained results have revealed that the heat transfer enhancement depends on the baffle position.

Slip effects on unsteady non-Newtonian blood flow through an inclined catheterized overlapping stenotic artery

Abstract: Slip effects on unsteady non-Newtonian blood hydro-magnetic flow through an inclined catheterized overlapping stenotic artery are analyzed. The constitutive equation of power law model is employed to simulate the rheological characteristics of the blood. The governing equations giving the flow derived by assuming the flow to be unsteady and two-dimensional. Mild stenosis approximation is employed to obtain the reduced form of the governing equations. Finite difference method is employed to obtain the solution of the non-linear partial differential equation in the presence of slip at the surface. An extensive quantitative analysis is performed for the effects of slip parameter, Hartmann number, cathetered parameter and arterial geometrical parameters of stenosis on the quantities of interest such as axial velocity, flow rate, resistance impedance and wall shear stress. The streamlines for the blood flow through the artery are also included.