A very recent study of Patil et al. (2017) on the effects of steady mixed convection flow with an exponentially decreasing free stream velocity motivates this research investigation. The present analysis reveals the mixed convection impact over an exponentially decreasing free stream velocity in an unsteady incompressible laminar boundary layer flow involving the effects of suction or blowing and heat generation or absorption. By utilizing the appropriate non-similar transformations, the complex dimensional governing boundary layer equations are simplified into dimensionless equations. In order to prevail the mathematical convolutions in attaining the non-similar solutions at the leading edge of the streamwise coordinate as well as non-similarity variable ξ, the coalition of implicit finite difference scheme and the Quasi-linearization technique is used with the suitable step sizes along the streamwise and time directions. The effects of various dimensionless physical parameters over the momentum and thermal fields are examined. The range of the parameters studied in this analysis are taken as α(-0.5⩽α⩽1.0), ξ(0⩽ξ⩽1), τ(0⩽τ⩽1), ε(0.000001⩽ε⩽0.1), Ri(-3⩽Ri⩽10), Re(10⩽Re⩽250), A(-1⩽A⩽1) and Q(-1⩽Q⩽1). Further, the present numerical investigation is focussed towards unsteady flow and heat transfer characteristics. © 2017 Elsevier Ltd

Satyajit Roy

Department of Mathematics

Boundary layer flow

Convolution

Finite difference method

flow velocity

Laminar boundary layer

Mixed convection

FREE STREAM

HEAT SOURCE/SINK

UNSTEADY EFFECTS

WALL SUCTION

Buoyancy

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IIT Madras

International Journal of Heat and Mass Transfer

Current paper deals with the numerical study on steady triple diffusive mixed convection boundary layer flow for exponentially decreasing external flow velocity in presence of suction/injection. Such exponentially decreasing external flows have specific applications in diverging channel flows. The temperature of the vertical surface is assumed to be higher compared to the surrounded fluid temperature. In the triple diffusive flow, the solutal components are chosen as Sodium chloride and Sucrose and the components are added in the flow stream from below with various concentration levels. The concentrations of NaCl-Water and Sucrose-Water are assumed to be lower within the free stream compared to the species concentrations of NaCl-Water and Sucrose-Water near the wall. The coupled nonlinear partial differential equations governing the flow, thermal and species concentration fields are transformed using the non-similarity variables and solved numerically by an implicit finite difference scheme with quasi-linearization technique. The effects of wall suction/injection, Richardson number, decelerating parameter, ratio of buoyancy parameters and Schmidt numbers of both the solutal components on the fluid flow, thermal and species concentration fields are analyzed and discussed. Results indicate that the thickness of the momentum boundary layer is lower for suction compared to injection for the buoyancy opposing flow. The decelerating parameter has significant impact on the flow fields. Also, the species concentration boundary layer thickness decreases with the increase of Schmidt numbers and that increases with the ratio of buoyancy parameters for both the species components. Overall, the mass transfer rate is found to increase with Schmidt numbers approximately 10% and 64% for NaCl and Sucrose, respectively. © 2018 Elsevier Ltd

Triple diffusive mixed convection from an exponentially decreasing mainstream velocity

This article explores the influence of mixed convection in a steady incompressible laminar boundary layer flow for an exponentially decreasing free stream velocity in presence of surface mass transfer and heat source or sink. The nonlinear partial differential equations governing the flow and thermal fields are expressed in dimensionless form with the help of suitable non-similar transformations. The mathematical complexities in obtaining non-similar solutions at the leading edge of the streamwise coordinate as well as non-similarity variable ξ have overcome by using the implicit finite difference scheme in conjunction with Quasi-linearization technique by choosing an appropriate finer step sizes along the streamwise direction. The effects of various dimensionless physical parameters on velocity and thermal fields are analysed. © 2016 Elsevier Ltd

Influence of mixed convection in an exponentially decreasing external flow velocity

The objective of the present article is to investigate the Dufour (diffusion-thermo) and Soret (thermal diffusion) effects on the steady double diffusive mixed convection boundary layer flows over an impermeable exponentially stretching sheet in an exponentially moving free stream under the influence of chemically reactive species. The nonlinear partial differential equations governing the flow, temperature and species concentration fields are expressed in non-dimensional form with the help of suitable non-similar transformations. The resulting final non-dimensional set of coupled nonlinear partial differential equations is solved by using an implicit finite difference scheme in conjunction with the Newton's linearization technique. The effects of various governing parameters involved in the velocity, temperature and species concentration fields are discussed in this article. The results display that the streamwise co-ordinate ξ (non-similarity variable) profoundly influences the flow, thermal and concentration fields which reveal the accountability of non-similar solutions. Results also indicate that the Dufour number Df decreases the heat transfer coefficient while the Soret number Sr decreases the mass transfer coefficient. © 2016 Elsevier Ltd.

Thermal diffusion and diffusion-thermo effects on mixed convection from an exponentially impermeable stretching surface

The main objective of the present paper is to obtain non-similar solutions numerically for steady two dimensional double diffusive mixed convection boundary layer flows along a vertical semi-infinite permeable surface under the influence of convective boundary condition along with surface mass transfer. The nonlinear partial differential equations governing the flow, temperature, and species concentration fields are expressed in non-dimensional form using suitable non-similar transformations. The final non-dimensional set of coupled nonlinear partial differential equations is solved by using an implicit finite difference scheme in combination with quasi-linearization technique. The effects of various governing parameters involved on the velocity, temperature and species concentration profiles are discussed in the present paper. The results show that the streamwise co-ordinate ξ significantly influences the flow, thermal, and concentration fields which indicate the importance of non-similar solutions. Results indicate that buoyancy parameter (Ri) and the ratio of buoyancy forces parameter (N) enhance the skin friction coefficient and decrease the heat transfer coefficient. Also, it is observed that the increase of suction parameter (A = 1) causes the decrease in the magnitude of temperature and concentration profiles from their values for injection parameter (A = -1). In the present investigation, dual solutions are also obtained under similarity assumptions and compared with previously published work. © 2013 Published by Elsevier Ltd.

Influence of convective boundary condition on double diffusive mixed convection from a permeable vertical surface

An unsteady mixed convection boundary layer flow over a permeable non-linearly stretching vertical slender cylinder is considered to investigate the combined effects of buoyancy force and thermal diffusion in presence of surface mass transfer, where the slender cylinder is in line with the flow. The unsteadiness in the flow and temperature fields is caused by the continuously non-linearly stretching vertical slender cylinder. The governing boundary layer equations are transformed into a non-dimensional form by a group of non-similar transformations. The resulting system of coupled non-linear partial differential equations is solved by an implicit finite difference scheme in combination with the quasi-linearization technique. Numerical computations are performed to understand the physical situations of linear and non-linearly stretching surface for different values of parameters to display the velocity and temperature profiles graphically. The obtained results show that the buoyancy parameter λ and the Prandtl number Pr enhance the skin friction coefficient and the local Nusselt number. It is also shown that the suction parameter A (>0) is to decrease the velocity and temperature profiles, but injection parameter A (<0) does the reverse. Results are compared with previously published work and are found to be in excellent agreement. © 2011 Elsevier Ltd.

Computers and Fluids

Unsteady effects on mixed convection boundary layer flow from a permeable slender cylinder due to non-linearly power law stretching

In this article, a numerical investigation on a steady two-dimensional mixed convection boundary layer flow along a moving semi-infinite vertical plate is presented. The plate is assumed to move with a constant velocity in the direction of the flow. The influence of internal heat generation or absorption is also included in the analysis. The nonlinear partial differential equations governing the flow and thermal fields are written in nondimensional form using a suitable group of transformations. The final nondimensional set of coupled nonlinear partial differential equations is solved using an implicit finite difference scheme in combination with the quasi-linearization technique. The effects of various parameters on the velocity and temperature profiles are reported. In addition, numerical results are presented for the skin friction coefficient and the Nusselt number. The present results are compared with previously published work and are found to be in excellent agreement. © 2012 Taylor and Francis Group, LLC.

Journal	Data powered by TypesetInternational Journal of Heat and Mass Transfer
Publisher	Data powered by TypesetElsevier Ltd
ISSN	00179310
Open Access	No