Double-diffusive Boundary Layer Flow Research Articles

MHD mixed convection on an inclined stretching plate in Darcy porous medium with Soret effect and variable surface conditions

AbstractThis work is concerned with a steady 2D laminar MHD mixed convective flow of an electrically conducting Newtonian fluid with low electrical conductivity along with heat and mass transfer on an isothermal stretching semi-infinite inclined plate embedded in a Darcy porous medium. Along with a strong uniform transverse external magnetic field, the Soret effect is considered. The temperature and concentration at the wall are varying with distance from the edge along the plate, but it is uniform at far away from the plate. The governing equations with necessary flow conditions are formulated under boundary layer approximations. Then a continuous group of symmetry transformations are employed to the governing equations and boundary conditions which determine a set of self-similar equations with necessary scaling laws. These equations are solved numerically and similar velocity, concentration, and temperature for various values of involved parameters are obtained and presented through graphs. The momentum boundary layer thickness becomes larger with increasing thermal and concentration buoyancy forces. The flow boundary layer thickness decreases with the angle of inclination of the stretching plate. The concentration increases considerably for larger values of the Soret number and it decreases with Lewis number. The skin friction coefficient increases for increasing angle of inclination of the plate, magnetic and porosity parameters, however it decreases for rise of thermal and solutal buoyancy parameters. In this double diffusive boundary layer flow, Nusselt and Sherweed numbers increase for rise of thermal and solutal buoyancy parameters, Prandtl number, but they behave opposite nature in case of angle of inclination of the plate, magnetic and porosity parameters. The Sherwood number increases for increasing Lewis number but it decreases for increasing Soret number.

Effect of Thermal Radiation on an Unsteady Magnetohydrodynamic Double Diffusive Boundary Layer Flow past a Permeable Infinite Vertical Plate with Heat Source

In this paper, effect of radiation and heat source parameters on temperature, concentration and velocity profile of an electrically conducting fluid passing through an infinite permeable plate is investigated. The governing equation, which was based on the balanced mass, linear momentum, energy and species concentration, were non-dimensionalized to reduce the equations to system of ordinary differential equations. This was then solved by perturbation technique. Effects of radiation parameter, heat source parameter, and Schmidt parameter are analyzed. We observed that the velocity and concentration profiles increase with increase in radiation parameter and heat source parameter. The temperature profile increases with decrease in radiation parameter with increases boundary layer thickness.

Thermodiffusion effects on boundary layer flow of viscoelastic nanofluids over a stretching sheet with viscous dissipation and non-uniform heat source using hp-finite element method

This paper theoretically investigates the conjugate effects of viscous dissipation and non-uniform heat source/ sink on the double-diffusive boundary layer flow of a viscoelastic nanofluid over a stretching sheet. In this model, where binary nanofluid is used, the Brownian motion, thermophoresis and cross-diffusion are classified as the main mechanisms which are responsible for the enhancement of the convection features of the nanofluid. The boundary layer equations governed by the partial differential equations are transformed into a set of ordinary differential equations with the help of group theory transformations. Computations are made by the hp-Galerkin finite element method (FEM). The hp-FEM needs a smaller number of nodes and consequently, less computational time and less memory to achieve the same or even better accuracy than h-FEM. A detailed evaluation of the effects of the governing physical parameters on the velocity, temperature, solutal and nanoparticle concentration via graphical plots is conducted for two different cases, namely prescribed surface temperature (PST) and prescribed heat flux (PHF). The reduced Sherwood number (in PST-case) is observed to be increased with the effects of nanofluid and the modified Dufour parameter, whereas the contrary behaviour is computed for the surface solutal concentration in PHF-case. Heat transfer is increasing function of viscoelastic parameter and decreasing function of Brownian motion, thermophoresis, space and time dependent heat source/sink parameter and Eckert number. Mass transfer is increasing function of Eckert number, space and time dependent heat source/sink parameter and decreasing function of viscoelastic parameter.

Finite element solution of double-diffusive boundary layer flow of viscoelastic nanofluids over a stretching sheet

This paper deals with the double-diffusive boundary layer flow of non-Newtonian nanofluid over a stretching sheet. In this model, where binary nanofluid is used, the Brownian motion and thermophoresis are classified as the main mechanisms which are responsible for the enhancement of the convection features of the nanofluid. The boundary layer equations governed by the partial differential equations are transformed into a set of ordinary differential equations with the help of group theory transformations. The variational finite element method (FEM) is used to solve these ordinary differential equations. We have examined the effects of different controlling parameters, namely, the Brownian motion parameter, the thermophoresis parameter, modified Dufour number, viscoelastic parameter, Prandtl number, regular Lewis number, Dufour Lewis number, and nanofluid Lewis number on the flow field and heat transfer characteristics. Graphical display of the numerical examine are performed to illustrate the influence of various flow parameters on the velocity, temperature, concentration, reduced Nusselt, reduced Sherwood and reduced nanofluid Sherwood number distributions. The present study has many applications in coating and suspensions, movement of biological fluids, cooling of metallic plate, melt-spinning, heat exchangers technology, and oceanography.

Finite element solution of double-diffusive boundary layer flow of viscoelastic nanofluids over a stretching sheet

Finite element solution of double-diffusive boundary layer flow of viscoelastic nanofluids over a stretching sheet

Influence of Fluctuating Surface Temperature and Concentration on Natural Convection Flow from a Vertical Flat Plate

A linearized theory is used to investigate how a free double-diffusive boundary layer flow is affected by small amplitude temporal variations in the surface temperature and species concentration. The mean temperature and the mean species concentration are assumed to vary as a power n of the distance measured from the leading edge. Three distinct methods, namely, a perturbation method for low frequencies, an asymptotic series expansion for high frequencies, and a finite difference method for intermediate frequencies, are used. Calculations have been carried out for a wide range of parameters in order to examine the results obtained from the three methods. Comparisons are made in. terms of the amplitudes and phases of the surface. heat transfer and surface mass transfer. It has been found that the amplitudes and phase angles predicted by perturbation theory and the asymptotic method are in good agreement with the finite difference computations.

Redistribution of phenocrysts by convective flow in a viscous boundary layer

The distribution of crystals suspended in the cooling margins of a magmatic intrusion is influenced not only by the temperature gradient but also by the dispersive forces related to velocity gradients in the convecting magma. The conditions in such a boundary layer are functions of several complexly inter-related factors. The velocity next to a steep wall is governed by the viscosity distribution, but the latter is strongly affected by the concentration of crystals, which in turn is determined in large part by the velocity gradient. These relations have been modelled mathematically to determine the equilibrium distribution of suspended crystals under a condition of uniform dispersive shear pressure across the width of a momentum boundary layer. The first-order effect is to sweep crystals from the wall toward the center of a plug-like velocity gradient, while crystals that nucleate and grow farther from the wall will move into the interior of the intrusion. Transfer of crystals up a temperature gradient by this mechanism can enhance fractionation and augment the efficiency of differentiation by double-diffusive boundary-layer flow.