Hartmann number

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

A computational analysis of heat transport irreversibility phenomenon in a magnetized porous channel

Abstract: The purpose of this paper is to evaluate the temperature, the Dirichlet conditions have been considered to the parallel horizontal plates. The model of generalized Brinkman-extended Darcy with the Boussinesq approximation is considered and the governing equations are computed by COMSOL multiphysics.,In the current study, the thermodynamic irreversible principle is applied to study the unsteady Poiseuille–Rayleigh–Benard (PRB) mixed convection in a channel (aspect ratio A = 5), with the effect of a uniform transverse magnetic field.,The effects of various flow parameters on the fluid flow, Hartmann number (Ha), Darcy number (Da), Brinkman number (Br) and porosity (e), are presented graphically and discussed. Numerical results for temperature and velocity profiles, entropy generation variations and contour maps of streamlines, are presented as functions of the governing parameter mentioned above. Basing on the generalized Brinkman-extended Darcy formulation, which allows the satisfaction of the no-slip boundary condition on a solid wall, it is found that the flow field and then entropy generation is notably influenced by the considering control parameters. The results demonstrate that the flow tends toward the steady-state with four various regimes, which strongly depends on the Hartman and Darcy numbers variations. Local thermodynamic irreversibilities are more confined near the active top and bottom horizontal walls of the channel when increasing the Da and decreasing the Hartmann number. Entropy generation is also found to be considerably affected by Brinkman number variation.,In the present work, we are presenting our investigations on the influence of a transverse applied external magnetohydrodynamic on entropy generation at the unsteady laminar PRB flow of an incompressible, Newtonian, viscous electrically conducting binary gas mixture fluid in porous channel of two horizontal heated plates. The numerical solutions for the liquid velocity, the temperature distribution and the rates of heat transport and entropy generation are obtained and are plotted graphically.

Optimal growth and transition to turbulence in channel flow with spanwise magnetic field

Abstract: Instability and transition to turbulence in a magnetohydrodynamic channel flow are studied numerically for the case of a uniform magnetic field imposed along the spanwise direction. Optimal perturbations and their maximum amplifications over finite time intervals are computed in the framework of the linear problem using an iterative scheme based on direct and adjoint governing equations. It is shown that, at sufficiently strong magnetic field, the maximum amplification is no longer provided by classical streamwise rolls, but rather by rolls oriented at an oblique angle to the basic flow direction. The angle grows with the Hartmann number Ha and reaches the limit corresponding to purely spanwise rolls at Ha between 50 and 100 depending on the Reynolds number. Direct numerical simulations are applied to investigate the transition to turbulence at a single subcritical Reynolds number Re = 5000 and various Hartmann numbers. The transition is caused by the transient growth and subsequent breakdown of optimal perturbations, which take the form of one or two symmetric optimal modes (streamwise, oblique or spanwise modes depending on Ha) with low-amplitude three-dimensional noise added at the moment of strongest energy amplification. A sufficiently strong magnetic field (Ha larger than approximately 30) is found to completely suppress the instability. At smaller Hartmann numbers, the transition is observed but it is modified in comparison with the pure hydrodynamic case.

Magnetohydrodynamic (MHD) flow of Sisko fluid near the axisymmetric stagnation point towards a stretching cylinder

Abstract: This paper investigates the momentum and heat transfer, MHD mixed convection flow of Sisko fluid near the axisymmetric stagnation point towards a stretching cylinder. Suitable similarity variables are selected to transmute dimensional nonlinear system into non-dimensional nonlinear system. Large mesh size and high tolerance error is considered for the convergence analysis of the numerical scheme. Graphical evaluation is displayed in order to interrogate the intrinsic behavior of responsible parameters on concerning profiles. For better description of fluid flow numerical variation in local skin friction coefficient and local Nusselt number is scrutinized through graphs and tables. Appreciable growth is found in temperature profile whereas a decrease in velocity profile is noticed when the Hartmann number is augmented. Mixed convection and velocity ratio parameters serve to enhance the rate of heat transfer from the surface. Comparison of present work in a limiting case with data available in the literature has been made for the verification of the model.

Hydromagnetic flow of fluid with variable viscosity in a uniform tube with peristalsis

Abstract: We formulate this problem under an infinitely long wavelength approximation, a negligible Reynolds number and a small magnetic Reynolds number. We decide on a perturbation method of solution. The viscosity parameter α 1 is chosen as a perturbation parameter. The governing equations are developed up to first-order in the viscosity parameter (α). The zero-order system yields the classical Poiseuille flow when the Hartmann number M tends to zero. For the first-order system, we simplify a complicated group of products of Bessel functions by approximating the polynomial. The results show that the increasing magnetic field increases the pressure rise. In addition, the pressure rise increases as the viscosity parameter decreases at zero flow rate. Moreover, it is independent of the Hartmann number and viscosity parameter at certain values of flow rate. We make comparisons with other studies.