An exact solution to the problem of MHD transient free convection and mass transfer flow of a viscous, incompressible, and electrically conducting fluid past a suddenly started infinite vertical plate taking into account the thermal diffusion as well as the thermal radiation is presented. Assuming the medium to be nonscattered and the fluid to be nongray, emitting–absorbing, and optically thin radiation limit properties, the equations governing the flow and heat and mass transfer are solved by Laplace transform technique. The expressions for the velocity field, the concentration field, the skin friction at the plate in the direction of the flow, and the coefficient of heat transfer and mass transfer from the plate to the fluid have been obtained, and their numerical values for different values of the physical parameters involved in the problem have been demonstrated in graphs and tables, and these are physically interpreted. It is found that the thermal radiation retards the fluid flow whereas the Soret effect accelerates the flow. The viscous drag on the plate is increased under the Soret and magnetic field effects whereas the thermal radiation reduces the skin friction. Further, the rate of heat transfer at the plate increases under thermal radiation effect. Also, in the presence of radiation, the Soret effect results in a steady increase in the mass flux from the fluid to the plate.

In this study, we investigate the heat and mass transfer in MHD convective flow past an infinite plate, through a porous media in presence of radiation, diffusion-thermo effect, and heat sink. A uniform magnetic field is applied transversely in the fluid region. The novelty of the present work is to analyze the diffusion-thermo effect on the flow phenomena in the presence of heat sink and thermal radiation. The governing equations are solved by perturbation technique to get expressions for velocity, temperature, and concentration fields. The influence of various physical quantities on the flow domain is studied graphically and in tabular form. It has been found that when heat flux is generated due to temperature gradient, the fluid velocity increases whereas the fluid temperature falls due to the diffusion-thermo effect. The current results have been compared with the existing results in some cases and it has been found that the findings of the present study are consistent with earlier findings.

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An attempt has been made to study the unsteady MHD free convective flow past a vertical porous plate immersed in a porous medium with Hall current, thermal diffusion and heat source. Analytical solution has been found depending on the physical parameters including the Hartmann number M, the Prandtl number Pr, the Grashof number for heat transfer Gr , the Grashof number for mass transfer Gc , the Schmidt number Sc , the Hall parameter m, the Soret number 0 S , heat source S , frequency parameter Ω . The influence of these parameters on velocity, temperature, species concentration, and shearing stress at the plate are demonstrated graphically and the results obtained are discussed. It is found that the concentration at the plate-surface increases under Soret effect. Further, it is observed that the Soret effect causes the main-flow shear stress to rise and the crossflow shear stress to fall. It is also found that a decrease in the Soret effect leads to an increase in both the main flow and crossflow velocities.2000 Mathematics subject classification: 76 W 05

In this paper, a theoretical study of a three‐dimensional mixed convective mass transfer flow past a semi‐infinite vertical plate embedded in a porous medium has been presented. The novelty of the present work is to analyze the influence of periodic permeability on the flow and transport characteristics in the presence of viscous dissipation and chemical reaction. The equations governing the flow, heat, and mass transfer are solved analytically by using asymptotic series expansion method. The variations in fluid velocity, temperature, and concentration fields due to change of various physical parameters are demonstrated graphically, whereas the numerical values of skin friction and the rate of mass transfer at the plate are compiled in tabular form. It is found that fluid velocity is increased for increasing permeability. Further, it is seen that concentration level of the fluid drops due to chemical reaction.

The problem of a hydromagnetic convective flow of an electrically incompressible viscous conducting fluid past a uniformly moving vertical porous plate is investigated analytically, taking into consideration radiation and thermal diffusion effects. A constant suction velocity is applied to the plate. A uniformly strong magnetic field is supposed to be applied normally to the plate and directed into the fluid region. To find a solution to the problem, an asymptotic series expansion method is used. The effects of thermal diffusion, magnetic field, porosity parameter, thermal radiation, and Grashof number are mainly focused on the discussion of the current problem. Increasing Soret number (Sr) hikes the velocity profile and skin friction but declines Sherwood number. Also, it has been found that, when the magnetic parameter (M) increased, the fluid velocity and the concentration profile decreased.The current results show a good deal of agreement with previously published work. The findings of this study could be relevant in a variety of applications, including diffusion processes involving molecular diffusion of species with molar concentration.

In this paper, the Soret and Dufour effects on a mixed convective mass transfer flow past an infinite vertical porous plate with transverse sinusoidal suction velocity in presence of a uniform transverse magnetic field have been studied analytically. The magnetic Reynolds number is assumed to be so small that the induced magnetic field can be neglected. The nondimensional equations governing the flow and heat and mass transfer are solved by regular perturbation technique, on the assumption that the solution consists of two parts: a mean part and a perturbed part. The expressions for the velocity, temperature and concentration fields, skin friction at the plate in the direction of the free stream, Nusselt number and Sherwood number at the plate, and the current density are obtained in nondimensional forms. The effects of the Hartmann number M, the Soret number Sr, the Dufour number Du, the Reynolds number Re, Schmidt number Sc, and the Prandtl number Pr on the flow and transport characteristics are discussed through graphs and tables. It is seen that viscous drag on the plate is reduced under the effect of thermal-diffusion (Soret) and diffusion-thermo (Dufour). On the other hand, the rate of heat transfer from the plate to the fluid falls because of the Dufour effect and rises under the Soret effect, whereas the mass flux from the plate to the fluid is delayed under the thermal-diffusion effect, but the reverse occurs under the effect of diffusion-thermo.

The present investigation aims to find an exact solution to the problem of a free convective, viscous, radiating, chemically reacting, optically thick, non-gray, and incompressible MHD flow past an exponentially accelerated semi-infinite vertical plate in presence of a transverse magnetic field. The medium of flow is porous. Arbitrary ramped temperature and diffusion thermo effects are also considered. Rosseland approximation method is used to describe the flux that appears in the energy equation. The effects of different parameters on flow and transport characteristics are discussed with the help of suitable graphs. It is noticed that velocity field and concentration field decreases but temperature field increases with an upsurge in Schmidt number. Also, Nusselt number and skin friction rise with increasing chemical reaction parameter but lowers with increasing radiation parameter. Faster consumption of chemical substances decelerates both concentration and velocity but accelerates temperature of the fluid. An interesting outcome outcome of our investigation is that both Dufour effect and arbitrary ramped temperature diminishes fluid velocity.