Showing papers on "Hartmann number published in 1980"

The primary electroviscous effect in a suspension of rods

Abstract: Previous studies of the distortion of the electric double layer around a charged sphere have assumed that the electric stresses are small compared with the viscous stresses. The flow around the particle is therefore changed only slightly by the presence of the charge cloud. This change is measured by the Hartmann number, and in § 6 we remove the restriction that it should be small. It is found that the previous linearized theory is sufficiently accurate for typical experimental values of the Hartmann number. Previous studies have also assumed that the potential at the surface of the particle is small. This assumption is removed in § 7 of this paper. For values of the non-dimensional surface potential smaller than 2 the predictions are altered by less than 10 %. For higher values the differences between linear and nonlinear theory are not negligible, especially when the charge cloud is thin compared with the radius of the charged sphere.

Effects of mass transfer on the hydromagnetic free convective flow in the Stokes' problem

Abstract: The effects of the mass transfer on free convection flow of an electrically conducting viscous fluid (e.g., of a stellar atmosphere) past an impulsively started infinite vertical limiting surface (e.g., of a star) in presence of a transverse magnetic field is considered. Solutions for the velocity and skin-friction, in closed form are obtained with the help of the Laplace transform technique and the results obtained for various values of the parametersSc (Schmidt number),P (Prandtl number) andM (Hartmann number) are given in graphical form. The paper is concluded with a discussion of the results obtained.

Effect of conducting walls on the dispersion of soluble matter in mhd channel flow

Abstract: An exact analysis of the dispersion of a solute in an incompressible electrically conducting fluid flowing between two electrically conducting parallel plates permeated by a transverse magnetic field is presented in this paper. A generalized dispersion model which is valid for all time has been used. It is found that for fixed Hartmann number M, the time dependent dispersion co-efficient K2(τ) decreases with increase in the wall conductivity parameter φ. It is also found that the dispersion co-efficient remains unaltered if the two walls are interchanged.

The pipe end problem in thermoelectric MHD

Abstract: Thermoelectric currents due to temperature variations at the interface between a conducting liquid and a conducting container stir the fluid if a magnetic field is present. This paper extends previous work to the case where walls parallel to the magnetic field are present, the Hartmann number being high. The specific problems solved refer to a circular pipe under a uniform transverse magnetic field with plane conducting ends, parallel to the field. The Seebeck e.m.f. at the wall is taken to be a linear function of the Cartesian coordinates. Complex flow into and out of the highspeed boundary layers on the ends occurs when the isotherms are parallel to the magnetic field. If the isotherms are perpendicular to the magnetic field, non-uniform rotation about the pipe axis occurs near the ends.

High Hartmann number flow through a rectangular duct with unequally and finitely conducting walls

Abstract: Nonsymmetric Hartmann flow through a rectangular duct is investigated for thin duct walls with, generally, unequal but finite conductivities. A high Hartmann number is adopted. Consistent with known phenomena, both Hartmann layers transverse to the applied magnetic field are assumed to be separated from the two side boundary layers by four corner regions plus four inner corner regions. The method of singular perturbations and matched asymptotic expansions is applied to the coupled system. The equations governing the core and Hartmann layers are first partially resolved for leading terms. This is then followed by tackling equations governing one side layer and two adjacent corner regions. The latters' incorporation secures, for the former, only those boundary conditions that are compatible along the transverse walls. Both corner regions are denied access to non-required boundary conditions along the neighbouring side wall by the adjoining inner corner regions. However, the latters' boundary value problems need not be tackled for the acquirement of only dominant terms beyond all four inner corner regions. The complementary side layer and associated corners are accounted for by a non-symmetric reflection principle. Results reveal that a difference between conductivities in the transverse walls together with at least one finitely conducting side wall impart to disturbances within the core and Hartmann layers (i) a nontrivial dependence on the transverse coordinate relative to the magnetic field and flow in addition to the (usual) dependence on the field aligned coordinate, (ii) a dependence on side wall parameters in addition to the dependence on transverse wall parameters. Applications to related situations are considered. These include the case for a perfectly conducting lower wall, a finitely conducting upper wall, and equally and finitely conducting side walls.

Diffusion to a particle at large Peclet numbers and small Reynolds and Hartmann numbers

Abstract: A study is made of the influence of a homogeneous magnetic field on the mass transfer for a spherical solid particle and a liquid drop in a flow of a viscous electrically conducting fluid. The previously obtained [1] velocity field of the fluid is used to calculate the concentration distribution in the diffusion boundary layer, the density of the diffusion flux, and the Nusselt number, which characterizes the mass transfer between the particle and the surrounding medium.