Kumari and Nath [9] have studied development **of** two-dimensional bound- ary layer with **an** applied magnetic field due to **an** impulsive motion. Muthuku- maraswamy and Ganesan [10] have studied **unsteady** **flow** **past** **an** impulsively started **vertical** **plate** with heat and mass transfer. Kim [11] presented **an** analysis **of** **an** **unsteady** **MHD** **convection** **flow** **past** a **vertical** moving **plate** embedded **in** a **porous** medium **in** **the** **presence** **of** transverse magnetic field. Helmy [12] studied **MHD** **unsteady** **free** **convection** **flow** **past** a **vertical** **porous** **plate**. Raptis [13] analyzed **the** thermal radiation and **free** **convection** **flow** through a **porous** medium bounded by a **vertical** infinite **porous** **plate** by using a regular perturbation technique. Pantokratoras [14] studied Non-Darcian forced **convection** heat transfer over a flat **plate** **in** a **porous** medium with variable viscosity and variable Prandtl number. Sacheti et al.[16] have stud- ied exact solutions for **unsteady** magneto-hydrodynamics **free** **convection** **flow** with constant heat flux. Ibrahim [?] studied **the** effects **of** **chemical** **reaction** and radiation absorption **on** transient hydro magnetic natural **convection** **flow** with wall transpiration and heat source. Anjalidevi and Kandasamy [17] have examined **the** **effect** **of** a **chemical** **reaction** **on** **the** **flow** **in** **the** **presence** **of** heat transfer and magnetic field. Mansour et al.[18] analyzed **the** **effect** **of** **chemical** **reaction** and viscous **on** **MHD** natural **convection** flows saturated **in** **porous** media with **suction** **or** **injection**. However, **in** engineering and technology, there are occasions where a heat source is needed to maintain **the** desired heat transfer. At **the** same time, **the** **suction** velocity has also to be normal to **the** **porous** **plate**.

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ous applications, hydromagnetic **free** **convection** **flow** **in** **the** stokes problem for a **porous** **vertical** limiting surface with constant **suction** has been analyzed by Nanousis et al. [8]. Singh [9] studied **MHD** **free** **convection** **flow** **in** **the** stokes problem for a **porous** **vertical** **plate**. Numerous scientists works **on** a similarity solution **of** **an** **unsteady** one-dimensional hydromagnetic heat transfer **flow** with variable **suction** **or** **injection**. **In** this study, a time depen- dent similarity parameter was introduced **on** **the** basis **of** **the** proposal put forward by Hasimoto [10]. Introducing this similarity parameter, **the** governing boundary layer equations were reduced to non-linear ordinary differential equations, which are similar **in** time. Later many articles have been published **in** this line, **the** works **of** which are Sattar and Hossain [11], Sattar [12], Sattar et al. [13], Alam et al. [14] and Rahman and Sattar [15] are worth mention- ing.

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H. L. Agarwal and P. C. Ram [1] have studied **the** effects **of** Hall Current **on** **the** hydro-magnetic **free** **convection** with mass transfer **in** a rotating fluid. H. S. Takhar and P. C. Ram [2] have studied **the** effects **of** Hall current **on** hydro-magnetic **free** convective **flow** through a **porous** medium. B. K. Sharma and A. K. Jha [3] have analyzed analytically **the** steady combined heat and mass transfer **flow** with induced magnetic field. B. P. Garg [4] has studied combined effects **of** thermal radiations and hall current **on** moving **vertical** **porous** **plate** **in** a rotating system with variable temperature. Dufour and Soret Effects **on** Steady **MHD** **Free** **Convection** and Mass Transfer Fluid **Flow** through a **Porous** Medium **in** A Rotating System have been investigated by Nazmul Islam and M. M. Alam [5]. Hall Current Effects **on** Magneto hydrodynamics Fluid over **an** Infinite Rotating **Vertical** **Porous** **Plate** Embedded **in** **Unsteady** Laminar **Flow** have been studied by Anika et al [6]. S. F. Ahmmed and M. K. Das [7] have investigated Analytical Study **on** **Unsteady** **MHD** **Free** **Convection** and Mass Transfer **Flow** **Past** a **Vertical** **Porous** **Plate**.

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boundary layer **flow** along a heated **vertical** flat **plate** embedded **in** a fluid-saturated **porous** medium, which was investigated by Cheng and Minkowycz (1977). They obtained similarity solutions for **the** case when wall temperature varies as a power function **of** **the** distance from **the** leading edge. Nakayama and Koyama (1987) analyzed combined **free** and forced **convection** **flow** **in** Darcian and non- Darcian **porous** medium. Lai and Kulacki (1991) studied non-Darcy mixed **convection** **flow** along a **vertical** wall **in** a fluid saturated **porous** medium. Hsieh et al. (1993) obtained non-similar solution for **free** and forced **convection** **flow** from a **vertical** surface **in** a **porous** medium. Rees (1999) analyzed **free** **convection** boundary layer **flow** from **an** isothermal **vertical** flat **plate** embedded **in** a fluid saturated layered **porous** medium. Jana et al. (2012) studied natural **convection** boundary layer **flow** from **an** inclined flat **plate** with finite dimensions embedded **in** a **porous** medium **in** a rotating environment. Khan and Pop (2013) investigated **the** Cheng and Minkowycz problem for triple diffusive natural **convection** boundary layer **flow** **past** a **vertical** **plate** **in** a **porous** medium. Reddy et al. (2013) studied **unsteady** hydromagnetic natural **convection** **flow** **past** a moving **vertical** **plate** **in** a **porous** medium **in** **the** **presence** **of** radiation and **chemical** **reaction**. Comprehensive reviews **of** convective **flow** **in** **porous** media are candidly presented **in** **the** form **of** books and monographs by Ingham and Pop (2002), Ingham et al. (2004), Vafai (2005) and Nield and Bejan (2006).

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accelerating surface with heat source **in** **presence** **of** **suction** and blowing. Kamel [9] investigated **the** **unsteady** **MHD** **convection** through a **porous** medium with combined heat and mass transfer **in** **presence** **of** heat source/sink. Devi and Kandaswamy [10] estimated **the** **effect** **of** **chemical** **reaction**, heat and mass transfer **on** non-linear **MHD** **flow** **past** **an** accelerating surface with heat source and thermal stratification **in** **the** **presence** **of** **suction** **or** **injection**.

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Sposito and Ciafalo (2006) studied fully developed **flow** **of** **an** electrically conducting fluid between parallel walls under **the** simultaneous influence **of** a driving pressure head, buoyancy and **MHD** forces, where **the** fluid was assumed to be internally heated and **the** **flow** was modeled as one-dimensional and incompressible. Al-Khawaja et al. (1994) solved numerically **the** problem **of** fully developed, laminar, steady, forced **convection** heat transfer **in** **an** electrically conducting fluid flowing **in** **an** electrically insulated, horizontal circular pipe **in** a **vertical** uniform transverse magnetic. Al-Khawaja et al. (1999) also studied **the** same problem for **free**- and-forced **convection** **flow** numerically using finite difference schemes for Grashof numbers 0 to 106 and Hartmaan numbers 0 to 500. Umavathi and Malashetty (2005) solved **the** problem **of** combined **free** and forced convective **MHD** **flow** **in** a **vertical** channel by taking into account **the** **effect** **of** viscous and ohmic dissipations, analytically by perturbation series method and numerically by finite difference technique. Umavathi and Chamkha (2011) analyzed **the** **effect** **of** heat and mass transfer **on** mixed convective **flow** **of** a viscous incompressible fluid **past** a **vertical** infinite **plate** **in** **the** **presence** **of** heat source **or** sink. Garandet and Alboussiere (1992) proposed analytical solutions to **the** equations **of** **MHD** that was used to model **the** **effect** **of** a transverse magnetic field **on** buoyancy driven **convection** **in** a two-dimensional cavity, **in** **the** case **of** high Hartmaan number limit. Blosseville et al. (2007) investigated analytically a fully developed buoyant **flow** **in** a straight, horizontal rectangular duct with **an** axial temperature gradient **in** **an** arbitrary oriented, transverse magnetic field with insulated walls. Aruna et al. (2011) studied **the** developed **MHD** mixed **convection** **flow** **in** a **vertical** channel, where **the** problem was described by means **of** partial differential equations and **the** solutions were obtained by **an** implicit finite difference technique coupled with a marching

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Transient natural **convection** is **of** fundamental interest **in** many industrial and environmental situations such as air conditioning systems, atmospheric flows, motors, thermal regulation process, cooling **of** electronic devices, and security **of** energy systems. Buoyancy is also **of** importance **in** **an** environment where differences between land and air temperatures can give rise to compli- cated **flow** patterns. Magnetohydrodynamic has attracted **the** attention **of** a large number **of** scholars due to its diverse applications. **In** astrophysics and geophysics, it is applied to study **the** stellar and solar structures, interstellar matter, radio propagation through **the** ionosphere etc. **In** engineering it finds its application **in** **MHD** pumps, **MHD** bearings etc. **Convection** **in** **porous** media has applications **in** geothermal energy recovery, oil extraction, thermal energy storage and **flow** through filtering devices. Convective heat transfer **in** **porous** media has received considerable attention **in** recent years owing to its importance **in** various technological applications such as fibre and granular insulation, electronic system cooling, cool combustors, and **porous** material regenerative heat exchangers. Books by Nield and Bejan [1], Bejan and Kraus [2] and Ingham et al. [3] excellently describe **the** extent **of** **the** research infor- mation **in** this area. **The** phenomena **of** mass transfer is also very common **in** theory **of** stellar structure and observable effects are detectable, at least **on** **the** solar surface. **The** study **of** effects **of** magnetic field **on** **free** **convection** **flow** is important **in** liquid-metals, electrolytes and ionized gases. **The** ther- mal physics **of** hydromagnetic problems with mass transfer is **of** interest **in** power engineering and metallurgy. Thermal radiation **in** fluid dynamics has become a significant branch **of** **the** engineering sciences and is **an** essential as- pect **of** various scenarios **in** mechanical, aerospace, **chemical**, environmental, solar power, and hazards engineering. Viscous mechanical dissipation effects are important **in** geophysical flows and also **in** certain industrial operations and are usually characterized by **the** Eckert number. **In** **the** literature, exten- sive research work is available to examine **the** **effect** **of** natural **convection** **on** **flow** **past** a **plate**.

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486 transfer. Afify (2009) discussed **the** **MHD** **free** convective heat and mass transfer **flow** over a stretching sheet **in** **the** **presence** **of** **suction**/**injection** with thermal diffusion and diffusion thermo effects. **The** influence **of** dust particles **on** **the** **flow** **of** a viscous fluid has several important applications. **The** dust particles tend to retard **the** **flow** and to decrease **the** fluid temperature. Such flows are encountered **in** a wide variety **of** engineering problem such as nuclear reactor cooling, rain erosion, paint spraying, transport, waste water treatment, combustion, etc. **The** **presence** **of** solid particles such as ash **or** soot **in** combustion energy generators and their **effect** **on** performance **of** such devices led to studies **of** particulate suspension **in** electrically conducting fluid **in** **the** **presence** **of** magnetic field. Saffman (1962) initiated **the** study **of** dusty fluids and discussed **the** stability **of** **the** laminar **flow** **of** a dusty gas **in** which **the** dust particles are uniformly distributed Chamkha (2000b) investigated **the** **unsteady** laminar hydromagnetic fluid particle **flow** and heat transfer **in** channels and circular pipes considering two phase continuum models. **The** effects **of** Hall current **on** **the** Couette **flow** with heat transfer **of** a dusty conducting fluid **in** **the** **presence** **of** uniform **suction**/**injection** was studied by Attia (2005). Ghosh and Ghosh (2008) considered **the** problem **of** hydromagnetic rotating **flow** **of** a dusty fluid near a pulsating **plate** when **the** **flow** is generated **in** **the** fluid particle system due to velocity tooth pulses subjected **on** **the** **plate** **in** **the** **presence** **of** a transverse magnetic field. Makinde and Chinyoka (2010) investigated **the** **unsteady** fluid **flow** and heat transfer **of** a dusty fluid between two parallel plates with variable viscosity and thermal conductivity

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When **the** temperature **of** surrounding fluid is high, **the** radiation effects play **an** im- portant role that cannot be ignored, Modest [28] and Siegel and Howell [29]. **The** effects **of** radiation **on** temperature have become more important industrialized. Many processes **in** en- gineering areas occur at high temperature and acknowledge radiation heat transfer become very important for **the** design **of** pertinent equipment. Nuclear power plants, gas turbines and **the** various propulsion devices for aircraft, missiles, satellites and space vehicles are examples **of** such engineering areas. **In** such cases one has to take into account **the** effects **of** radiation and **free** **convection**. For **an** impulsively started infinite **vertical** isothermal **plate**, Ganesan et al. [30] studied **the** effects **of** radiation and **free** **convection**, by using Rosseland approxima- tion, Brewster [31]. Problem **of** radiative heat transfer with hydromagnetic **flow** and viscous dissipation over a stretching surface **in** **the** **presence** **of** variable heat flux is solved analytically by Kumar [32]. Hossain and Takhar [33], Raptis and Massals [34], and Hossain et al. [35] studied **the** radiation **effect** **on** **free** and forced **convection** flows **past** a **vertical** **plate**, including various physical aspects. Aboeldahab Emad [36] studied **the** radiation **effect** **on** heat transfer **in** **an** electrically conducting fluid at **the** stretching surface. At high operating temperature, ra- diation **effect** can be quite significant, Ghaly and Elbarbary [37]. Heat and mass transfer ef- fects **on** moving **plate** **in** **the** **presence** **of** thermal radiation have been studied by Muthucuma- raswamy and Kumar [38] using Laplace technique. For **the** problem **of** coupled heat and mass transfer **in** **MHD** **free** **convection**, **the** **effect** **of** both viscous dissipation and ohmic heating are not studied **in** **the** previous investigations. However, it is more realistic to include these two effects to explore **the** impact **of** **the** magnetic field **on** **the** thermal transport **in** **the** boundary layer. With this awareness, **the** **effect** **of** ohmic heating **on** **the** **MHD** **free** **convection** heat transfer has been examined for a Newtonian fluid by Hossain [39]. Chen [40] studied **the** problem **of** combined heat and mass transfer **of** **an** electrically conducting fluid **in** **MHD** natu- ral **convection**, adjacent to a **vertical** surface with ohmic heating.

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It is interesting to note that **the** Brownian motion **of** nanoparticles at molecular and nanoscale levels are a key nanoscale mechanism governing their thermal behaviors. **In** nanofluid systems, due to **the** size **of** **the** nanoparticles, **the** Brownian motion takes place, which can affect **the** heat transfer properties. As **the** particle size scale approaches to **the** nanometer scale, **the** particle Brownian motion and its **effect** **on** **the** surrounding liquids play **an** important role **in** **the** heat transfer. **In** view **of** these applications, Nield and Kuznetsov ([22, 23]) analyzed **the** **free** convective boundary layer flows **in** a **porous** medium saturated by nanofluid by taking Brownian motion and thermophoresis effects into consideration. **In** **the** first article, **the** authors have assumed that nanoparticles are suspended **in** **the** nanofluid using either surfactant **or** surface charge technology and hence they have concluded that this prevents particles from agglomeration and deposition **on** **the** **porous** matrix. Chamkha et al. [24] carried out a boundary layer analysis for **the** natural **convection** **past** **an** isothermal sphere **in** a Darcy **porous** medium saturated with a nanofluid. Nield and Kuznetsov [25] investigated **the** cross-diffusion **in** nanofluids, with **the** aim **of** making a detailed comparison with regular cross diffusion effects and **the** cross- diffusion effects peculiar to nanofluids, and at **the** same time investigating **the** interaction between these effects when **the** base fluid **of** **the** nanofluid is itself a binary fluid such as salty water. Recently, a boundary layer analysis for **the** natural **convection** **past** a horizontal **plate** **in** a **porous** medium saturated with a nanofluid is analyzed by Gorla and Chamkha [26], N. Kishan et.al [27], studied **the** **unsteady** **MHD** **flow** **of** heat and mass transfer **of** Cu-water and TiO 2 -water nanofluids over stretching sheet with a non-uniform heat/source/sink

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design **of** heat exchangers, induction pumps, and nuclear reactors, **in** oil exploration and **in** space vehicle propulsion. Thermal radiation **in** fluid dynamics has become a significant branch **of** **the** engineering sciences and is **an** essential aspect **of** various scenarios **in** mechanical, aerospace, **chemical**, environmental, solar power and hazards engineering. Bhaskara Reddy and Bathaiah [18, 19] analyze **the** Magnetohydrodynamic **free** **convection** laminar **flow** **of** **an** incompressible Viscoelastic fluid. Later, he was studied **the** **MHD** combined **free** and forced **convection** **flow** through two parallel **porous** walls. Elabashbeshy [20] studied heat and mass transfer along a **vertical** **plate** **in** **the** **presence** **of** magnetic field. Samad, Karim and Mohammad [21] calculated numerically **the** **effect** **of** thermal radiation **on** steady **MHD** **free** convectoin **flow** taking into account **the** Rosseland diffusion approximaion. Loganathan and Arasu [22] analyzed **the** effects **of** thermophoresis particle deposition **on** non-Darcy **MHD** mixed convective heat and mass transfer **past** a **porous** wedge **in** **the** **presence** **of** **suction** **or** **injection**. Ghara, Maji, Das, Jana and Ghosh [23] analyzed **the** **unsteady** **MHD** Couette **flow** **of** a viscous fluid between two infinite non-conducting horizontal **porous** plates with **the** consideration **of** both Hall currents and ion-slip. **The** radiation **effect** **on** steady **free** **convection** **flow** near isothermal stretching sheet **in** **the** **presence** **of** magnetic field is investigated by Ghaly et al. [24]. Also, Ghaly [25] analyzed **the** **effect** **of** **the** radiation **on** heat and mass transfer **on** **flow** and thermal field **in** **the** **presence** **of** magnetic field for horizontal and inclined plates.

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High temperature thermal radiation **of** **an** optically thick gray gas becomes significant to **the** relevance **of** space technology **in** such way that **the** foundation **of** space laboratory **in** **the** zero gravity is established by **the** concept **of** gray body radiation. If **the** temperature **of** surrounding fluid is rather high, radiation effects play **an** important role and this situation does not exist **in** space technology. **In** such cases one has to take into account **the** **effect** **of** thermal radiation and mass diffusion. It takes place **in** numerous industrial applications, e.g. polymer production, manufacturing **of** ceramics **or** glassware, and food processing Cussler (1998). For some industrial applications such as glass production, furnace design, propulsion systems, plasma physics and spacecraft re-entry aerothermodynamics which operate at higher temperatures and radiation **effect** can also be significant. A clear understanding **of** **the** nature **of** interaction between thermal and concentration buoyancies is necessary. Consolidated effects **of** heat and mass transfer problems are **of** importance **in** many **chemical** formulations and reactive chemicals. Therefore, considerable attention had been paid **in** recent years to study **the** influence **of** **the** participating parameters **on** **the** velocity field. More such engineering application can be seeing **in** electrical power generation systems when **the** electrical energy is extracted directly from a moving conducting fluid. **The** study **of** magnetohydrodynamic **flow** for electrically conducting fluid **past** heated surface has attracted **the** interest **of** many researches **in** view **of** its important applications **in** many engineering problems such as plasma studies, petroleum industries **MHD** power generations, cooling **of** nuclear reactors, **the** boundary layer control **in** aerodynamics and crystal

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