International Journal of Thermophysics

, Volume 34, Issue 11, pp 2183–2208 | Cite as

Unsteady Flow of Radiating and Chemically Reacting MHD Micropolar Fluid in Slip-Flow Regime with Heat Generation

  • S.  M. Abo-Dahab
  • R.  A. Mohamed


An analytical study of the problem of unsteady free convection with thermal radiation and heat generation on MHD micropolar fluid flow through a porous medium bounded by a semi-infinite vertical plate in a slip-flow regime has been presented. The Rosseland diffusion approximation is used to describe the radiation heat flux in the energy equation. The homogeneous chemical reaction of first order is accounted for in the mass diffusion equation. A uniform magnetic field acts perpendicular on the porous surface absorbing micropolar fluid with a suction velocity varying with time. A perturbation technique is applied to obtain the expressions for the velocity, microrotation, temperature, and concentration distributions. Expressions for the skin-friction, Nusselt number, and Sherwood number are also obtained. The results are discussed graphically for different values of the parameters entered into the equations of the problem.


MHD Micropolar fluid Porous medium Thermal radiation  Heat generation Chemical reaction Slip-flow 

List of Symbols


Magnetic induction (\(T\))


Species concentration (\(\mathrm {mol}\,{\cdot }\,\mathrm {m}^{-3}\))

\(C_{\mathrm{w }}^{*}\)

Surface concentration (\(\mathrm {mol}\,{\cdot }\,\mathrm{m}^{-3}\))

\(C_{\infty }^{*}\)

Species concentration far from the surface (\(\mathrm {mol}\,{\cdot }\,\mathrm{m}^{-3}\))

\(C_\mathrm{f }\)

Skin-friction coefficient

\(C_\mathrm{m }\)

Couple stress coefficient


Specific heat at constant pressure (\(\mathrm J \,{\cdot }\, \mathrm{kg}^{-1}\,{\cdot }\, \mathrm K ^{-1}\))


Chemical molecular diffusivity (\(\mathrm m ^{2}\,{\cdot }\,\mathrm s ^{-1}\))


Solutal Grashof number


Grashof number


Accelaration due to gravity (\(\mathrm m \,{\cdot }\,\mathrm s ^{-2}\))


Dimensionless heat generation/absorption coefficient


Microinertia per unit mass (\(\mathrm m ^{2}\))


Permeability of the porous media (\(\mathrm m ^{2}\))


Mean absorption coefficient (\(\mathrm m ^{-1}\))


Diemnsionless permeability


Thermal conductivity of the fluid (\(\mathrm W \,{\cdot }\,\mathrm m ^{-1}\,{\cdot }\,\mathrm K ^{-1}\))


Local magnetic field parameter


Parameter related to microgyration vector and shear stress


Model parameter


Nusselt parameter


Pressure (\(\mathrm{kg}\,{\cdot }\,\mathrm m ^{-1}\,{\cdot }\,\mathrm s ^{-2}\))


Fluid Prandtl number


Heat generation coefficient (\(\mathrm W \,{\cdot }\,\mathrm m ^{-3}\,{\cdot }\,\mathrm K ^{-1}\))

\(q_\mathrm{r }^{*}\)

Radiative heat flux (\(\mathrm W \,{\cdot }\,\mathrm m ^{-2}\))


Reaction rate constant (J)


Radiation parameter


Reynolds number


Generalized Schmidt number


Sherwood number


Time (s)


Dimensionless time


Temperature in the boundary layer (K)

\(T_{\infty }^{*}\)

Temperature far away from the plate (K)

\(T_\mathrm w ^{*}\)

Temperature at the wall (K)


Dimensionless velocity

\(u^{*}\) and \(v^{*}\)

Velocities along and perpendicular to the plate (\(\mathrm m \,{\cdot }\,\mathrm s ^{-1}\))


Plate velocity in the direction of flow (\(\mathrm m \,{\cdot }\,\mathrm{s }^{-1}\))

\(U_{\infty }^{*}\)

Free stream velocity (\(\mathrm m \,{\cdot }\,\mathrm s ^{-1}\))


Knudsen number


Rarefaction parameter

\(\varrho \)

Characteristic dimension of flow


Scale of suction velocity

\(x^{*}\) and \(y^{*}\)

Distances along and perpendicular to the plate, respectively (m)


Dimensionless spanwise coordiante normal to the plate

\(\alpha \)

Fluid thermal diffusivity (\(\mathrm m ^{2}\,{\cdot }\,\mathrm s ^{-1}\))

\(\beta \)

Ratio of vortex viscosity and dynamic viscosity

\(\beta _{c}\)

Volumetric coefficient of thermal expansion (\(\mathrm K ^{-1}\))

\(\beta _\mathrm{f}\)

Volumetric coefficient of expansion with concentration (\(\mathrm K ^{-1}\))

\(\gamma \)

Spin-gradient velocity (\(\mathrm{kg}\,{\cdot }\,\mathrm m \,{\cdot }\,\mathrm s ^{-1}\))

\(\delta \)

Scalar constant

\(\epsilon \)

Scalar constant

\(\theta \)

Dimensionless temperature


Chemical reaction parameter

\(\eta \)

Scalar constant

\(\mu \)

Fluid dynamic viscosity (\(\mathrm{kg}\,{\cdot }\,\mathrm m ^{-1}\,{\cdot }\,\mathrm s ^{-1}\))

\(\nu \)

Fluid kinematic rotational viscosity (\(\mathrm m ^{2}\,{\cdot }\,\mathrm s ^{-1}\))

\(\nu _\mathrm{r}\)

Kinematic rotational viscosity (\(\mathrm m ^{2}\,{\cdot }\,\mathrm s ^{-1}\))

\(\rho \)

Fluid density (\(\mathrm{kg}\,{\cdot }\,\mathrm m ^{-3}\))

\(\sigma \)

Electrical conductivity of the fluid (\(\mathrm S \,{\cdot }\,\mathrm m ^{-1}\))

\(\sigma ^{*}\)

Stefan–Boltzmann constant (\(\mathrm W \,{\cdot }\,\mathrm m ^{-2}\,{\cdot }\,\mathrm K ^{-4}\))

\(\omega \)

Microrotation vector (\(\mathrm m \,{\cdot }\,\mathrm s ^{-1}\))

\(\varGamma \)

Coefficient of gryo-viscosity (or vortex viscosity) (\(\mathrm{kg}\,{\cdot }\,\mathrm m ^{-1}\,{\cdot }\,\mathrm s ^{-1}\))


Mean free path


Slip strength or slip coefficient


Maxwell’s reflection coefficient


Suction parameter


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Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  1. 1.Department of Mathematics, Faculty of ScienceSVUQena Egypt
  2. 2.Department of Mathematics, Faculty of ScienceTaif UniversityTaif Saudi Arabia

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