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PurposeThe purpose of this paper is to consider steady two‐dimensional mixed convection flow along a vertical semi‐infinite power‐law stretching sheet. The velocity and temperature of the sheet are assumed to vary in a power‐law form.Design/methodology/approachThe problem is formulated in terms of non‐similar equations. These equations are solved numerically by an efficient implicit, iterative, finite‐difference method in combination with a quasi‐linearization technique.FindingsIt was found that the skin‐friction coefficient increased with the ratio of free‐stream velocity to the composite reference velocity and the buoyancy parameter while it decreased with exponent parameter. The heat transfer rate increased with the Prandtl number, buoyancy parameter and the exponent parameter.Practical implicationsA very useful source of information for researchers on the subject of convective flow over stretching sheets.Originality/valueThis paper illustrates mixed convective flow over a power‐law stretched surface with variable wall temperature.

The principal objective of the present paper is to investigate the onset of convection in a horizontal layer heated from below which consists of distinct porous sublayers which are separated by solid heat-conducting partitions. Each of the porous sublayers are identical as are the solid partitions. The present analysis employs linearised stability theory and a dispersion relation is derived from which neutral curves may be computed. For two-layer configurations the dispersion relation may be written explicitly, but for larger numbers of sublayers a simple systematic numerical procedure is used to compute the dispersion relation which, while it may also be written analytically, rapidly becomes increasingly lengthy as the number of sublayers increases. It is found that neutral curves are always unimodal and each has a well-defined single minimum. We attempt to give a comprehensive physical understanding of the effect of the number of layer, the relative thickness of the partitions and the conductivity ratio on the onset of convection and the form taken by the onset modes. Our results are compared with those of Rees and Genç [1] who considered the special case where the partitions are infinitesimally thin.

Purpose -The purpose of this paper is to study the effects of surface mass transfer on the steady mixed convection flow from a vertical stretching sheet in a parallel free stream with variable wall temperature and concentration. Design/methodology/approach -An implicit finite difference scheme in combination with the quasilinearisation technique is employed to obtain non-similar solutions of the governing boundary layer equations for momentum, temperature and concentration fields. Findings -The numerical results are reported here to display the effects of mixed convection parameter, ratio of buoyancy forces, surface mass transfer (suction and injection), the ratio of free stream velocity to the composite reference velocity, Prandtl number and Schmidt number on velocity, temperature and concentration profiles as well as on skin friction, Nusselt number and Sherwood number. Research limitations/implications -Thermophysical properties of the fluid in the flow model are assumed to be constant except the density variations causing a body force term in the momentum equation. The Boussinesq approximation is invoked for the fluid properties to relate density changes, and to couple in this way the temperature and concentration fields to the flow field. The concentration of diffusing species is assumed to be very small in comparison with other chemical species far away from the surface. Hence the Soret and Dufour effects are neglected. The stretching sheet is assumed to be subject to a power-law wall temperature as well as to a power-law wall concentration, in a parallel free stream. Practical implications -Convective heat and mass transfer over a vertical stretching sheet in a parallel stream is very important for various design of technological process are hot rolling, wire drawing, glass-fiber paper production, both metal and polymer sheets, for instance, in cooling of an infinite metallic plate in a cooling bath, the boundary layer along material handling conveyors, etc. Originality/value -The paper studies the combined effects of thermal and mass diffusion over a vertical stretching sheet with surface mass transfer.

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