MHD AND HEAT TRANSFER IN A THIN FILM OVER AN UNSTEADY STRETCHING SURFACE WITH

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MHD AND HEAT TRANSFER IN A THIN FILM OVER AN UNSTEADY STRETCHING SURFACE WITH Powered By Docstoc
					International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
 INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME
                            AND TECHNOLOGY (IJMET)

ISSN 0976 – 6340 (Print)
ISSN 0976 – 6359 (Online)                                                        IJMET
Volume 4, Issue 4, July - August (2013), pp. 387-400
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    MHD AND HEAT TRANSFER IN A THIN FILM OVER AN UNSTEADY
    STRETCHING SURFACE WITH COMBINED EFFECT OF VISCOUS
          DISSIPATION AND NON-UNIFORM HEAT SOURCE

                  Anand H. Agadi1*, M. Subhas Abel2 and Jagadish V. Tawade3
    1*
       Department of Mathematics, Basaveshwar Engineering College, Bagalkot-587102, INDIA
           2
             Department of Mathematics, Gulbarga University, Gulbarga- 585 106, INDIA
     3
       Department of Mathematics, Bheemanna Khandre Institute of Technology, Bhalki-585328



ABSTRACT

        We have studied two-dimensional flow of a thin film over a horizontal stretching surface.
The flow of a thin fluid film and subsequent heat transfer from the stretching surface is investigated
with the aid of similarity transformation. The transformation enables to reduce the unsteady
boundary layer equations to a system of non-linear ordinary differential equations. Numerical
computation for the resulting nonlinear differential equations is obtained by Runge-Kutta fourth
order method with efficient shooting technique, which agrees well with the analytic solution. It is
shown that the heat fluxes from the liquid to the elastic sheet decreases with S for Pr ≤ 0.1 and
increases with S for Pr ≥ 1 . Some important findings reported in this work reveals that the effect of
non-uniform heat source have significant impact in controlling rate heat transfer in the boundary
layer region.

Key words:     Eckert number, MHD, Prandtl number, thin film, unsteady stretching surface.

1. INTRODUCTION

        The study of the flow resulting from a stretching boundary is important in process industry
such as the extrusion of sheet material into the coolant environment. The tangential velocity imparted
by the stretching sheet induces motion in the extruding fluid which ultimately solidified and formed
a sheet. In fact, stretching imparts a unidirectional orientation to the extrudate, thereby improving its
mechanical properties and the quality of the final product. Crane [1] first modeled this flow
configuration as a steady two-dimensional boundary layer flow caused by the stretching of a sheet
which moves in its own plane with velocity varying with distance from the slit and obtained an exact

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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME

solution analytically. This simple configuration has attracted several researchers [2 - 6] for the last
four decades and is extensively studied.
         The hydrodynamics of the finite fluid domain ( thin liquid film), over a stretching sheet was
first considered by Wang [8] who reduced the unsteady Nervier–Stokes equations to a nonlinear
ordinary differential equations by means of similarity transformation and solved the same using a
kind of multiple shooting method (see Robert and Shipman [9]). Wang [10] himself has used
homotopy analysis method to reinvestigate the thin film flow over a stretching sheet. Of late the
works of Wang [8] to the case of finite fluid domain are extended by several authors [11-15] for
fluids of both Newtonian and non-Newtonian kinds using various velocity and thermal boundary
conditions.
        Motivated by all these works we contemplate to study the effects of non-uniform heat source,
and viscous dissipation in presence of thermal radiation on the flow and heat transfer in a thin liquid
film over an unsteady stretching sheet, which is subjected to an external magnetic field.

2. MATHEMATICAL FORMULATION

        Let us consider a thin elastic sheet which emerges from a narrow slit at the origin of a
Cartesian co-ordinate system for investigations as shown schematically in Fig 1. The continuous
sheet at y = 0 is parallel with the x-axis and moves in its own plane with the velocity

                          bx
        U ( x, t ) =                                                                        (1)
                       (1 − α t )

where b and α are both positive constants with dimension per time. The surface temperature Ts of
the stretching sheet is assumed to vary with the distance x from the slit as

                                 bx 2            −
                                                     3
        Ts ( x, t ) = T0 − Tref        (1 − α t ) 2                                      (2)
                                 2υ 

Where T0 is the temperature at the slit and Tref can be taken as a constant reference temperature such
                                bx 2
that 0 ≤ Tref ≤ T0 . The term             can be recognized as the Local Reynolds number based on the
                             υ (1 − α t )
surface velocity U . The expression (1) for the velocity of the sheet U ( x, t ) reflects that the elastic
sheet which is fixed at the origin is stretched by applying a force in the positive x-direction and the
                              b
effective stretching rate            increase with time as 0 ≤ α < 1 . The applied transverse magnetic
                          (1 − α t )
field is assumed to be of variable kind and is chosen as

                                        1
                                    −
        B ( x, t ) = B0 (1- α t ) 2 .                                                       (3)

       The sheet is assumed to have velocity U as defined in equation (1) and the flow field is
exposed to the influence of an external transverse magnetic field of strength B as defined in equation
(3). The velocity and temperature fields of the liquid film obey the following boundary layer
equations


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        ∂u ∂v
          +   = 0,                                                                         (4)
        ∂x ∂y

        ∂u   ∂u  ∂u   ∂ 2u σ B 2
           +u +v    =υ 2 −       u,                                                        (5)
        ∂t   ∂x  ∂y   ∂y    ρ

                                                                   2
        ∂T    ∂T    ∂T   k ∂ 2T      µ  ∂u      q′′′
           +u    +v    =        2
                                  +         +                                            (6)
        ∂t    ∂x    ∂y ρ C p ∂y     ρ C p  ∂y  ρ C p

The non-uniform heat source/sink (see [30]) is modeled as

                 kuw ( x )
        q′′′ =             [ A * (Ts − T0 ) f ′ + (T − T0 ) B*],                           (7)
                   xυ

        Where A* and B* are the coefficients of space and temperature dependent heat source/sink
respectively. Here we make a note that the case A* > 0, B* > 0 corresponds to internal heat
generation and that A* < 0, B* < 0 corresponds to internal heat absorption.
The associated boundary conditions are given by

        u =U,         v = 0,         T = Ts    at    y = 0,                                (8)

        ∂u ∂T
          =   =0               at     y = h,                                               (9)
        ∂y ∂y

             dh
        v=             at    y = h.                                                      (10)
             dt

        At this juncture we make a note that the mathematical problem is implicitly formulated only
for x ≥ 0 . Further it is assumed that the surface of the planar liquid film is smooth so as to avoid the
complications due to surface waves. The influence of interfacial shear due to the quiescent
atmosphere, in other words the effect of surface tension is assumed to be negligible. The viscous
                    ∂u                              ∂T 
shear stress τ = µ   and the heat flux q = − k          vanish at the adiabatic free surface
                    ∂y                              ∂y 
(at y = h).
We now introduce dimensionless variables f and θ and the similarity variable η as

                     ψ ( x, y, t )                                                       (11)
        f (η ) =               1
                                      ,
                     υb      2
                          x
                    1−αt 

                               1
                b       2                                                              (12)
       η =               y.
           υ (1 − α t ) 
                        



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                       T0 − T   (x, y,t )                                                  (13)
       θ (η   )=                                    ,
                                               
                                 bx 2
                   T ref                       
                                           3
                          2 υ (1 − α t ) − 2   
                                                
                                               


       The physical stream function ψ ( x, y, t ) automatically assures mass conversion given in
equation (4). The velocity components are readily obtained as:

              ∂ψ  bx 
       u=       =          f ′ (η ) ,                                                    (14)
              ∂y  1 − α t 

                                        1
            ∂ψ     υb  2
        v=−    = −        f (η ) .                                                       (15)
            ∂x     1− αt 

        The mathematical problem defined in equations (4) – (6) and (8) – (9) transforms exactly into
a set of ordinary differential equations and their associated boundary conditions:

                η               2
        S  f ′ + f ′′  + ( f ′ ) − ff ′′ = f ′′′ − Mnf ′,                                (16)
                2 

           S                               
        Pr  ( 3θ + ηθ ′ ) + 2 f ′θ − θ ′ f  = θ ′′ − Ec Pr f ′′2 − ( A * f ′ + B *θ ),   (17)
           2                               

        f ′(0) = 1,          f (0) = 0,             θ (0) = 1,                             (18)

        f ′′( β ) = 0,      θ ′( β ) = 0,                                                  (19)

                   Sβ
        f (β ) =      .                                                                    (20)
                    2

                   α
       Here S ≡        is the dimensionless measure of the unsteadiness and the prime indicates
                   b
differentiation with respect toη . Further, β denotes the value of the similarity variable η at the free
surface so that equation (12) gives
                                1
                 b       2                                                               (21)
        β =               h.
            υ (1 − α t ) 
                         

       Yet β is an unknown constant, which should be determined as an integral part of the
boundary value problem. The rate at which film thickness varies can be obtained differentiating
equation (21) with respect to t, in the form




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                                         1

          dh    αβ       υ       2                                                                          (22)
          dt
             =−    
                    b (1 − α t )  .
                 2               
                                  

        Thus the kinematic constraint at y = h(t ) given by equation (10) transforms into the free
surface condition (22). It is noteworthy that the momentum boundary layer equation defined by
equation (16) subject to the relevant boundary conditions (18) – (20) is decoupled from the thermal
field; on the other hand the temperature field θ (η ) is coupled with the velocity field f (η ) . Since the
sheet is stretched horizontally the convection least affects the flow and hence there is a one-way
coupling of velocity and thermal fields.

3. NUMERICAL SOLUTION

        The non-linear differential equations (16) and (17) with appropriate boundary conditions
given in (18) to (20) are solved numerically, by the most efficient numerical shooting technique with
fourth order Runge–Kutta algorithm (see references [16]). The non-linear differential equations (16)
and (17) are first decomposed to a system of first order differential equations in the form

 df 0               df1               df 2          η             2
      = f1 ,            = f2 ,             = S  f1 + f 2  + ( f1 ) − f 0 f 2 +Mnf1 ,
 dη                 dη                dη            2 
                                                                                                              (25)
 dθ 0              d θ1   S                                                                          
      = θ1 ,           =  Pr  ( 3θ 0 + ηθ1 ) + 2 f1θ 0 − θ1 f 0  − Ec Pr f 2 2 + ( A * f ′ + B * θ )  .
 dη                dη   2                                                                            

Corresponding boundary conditions take the form,

          f1 (0) = 1,        f 0 (0) = 0,    θ 0 (0) = 1,                                                     (26)

          f 2 ( β ) = 0,     θ1 ( β ) = 0,                                                                    (27)

                      Sβ
          f0 (β ) =      .                                                                                    (28)
                       2

        Here f 0 (η ) = f (η ) and θ 0 (η ) = θ (η ). The above boundary value problem is first converted
into an initial value problem by appropriately guessing the missing slopes f 2 (0) and θ1 (0) . The
resulting IVP is solved by shooting method for a set of parameters appearing in the governing
equations and a known value of S. The value of β is so adjusted that condition (28) holds. This is
done on the trial and error basis. The value for which condition (28) holds is taken as the appropriate
film thickness and the IVP is finally solved using this value of β. The step length of h = 0.01 is
employed for the computation purpose. The convergence criterion largely depends on fairly good
guesses of the initial conditions in the shooting technique. The iterative process is terminated until
the relative difference between the current and the previous iterative values of f ( β ) matches with
                Sβ
the value of          up to a tolerance of 10 −6 . Once the convergence in achieved we integrate the
                 2
resultant ordinary differential equations using standard fourth order Runge–Kutta method with the
given set of parameters to obtain the required solution.


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4. RESULTS AND DISCUSSION

        The exact solution do not seem feasible for a complete set of equations (16)-(17) because of
the non linear form of the momentum and thermal boundary layer equations. This fact forces one to
obtain the solution of the problem numerically. Appropriate similarity transformation is adopted to
transform the governing partial differential equations of flow and heat transfer into a system of non-
linear ordinary differential equations. The resultant boundary value problem is solved by the efficient
shooting method. It is note worthy to mention that the solution exists only for small value of
unsteadiness parameter 0 ≤ S ≤ 2 . Moreover, when S → 0 the solution approaches to the analytical
solution obtained by Crane [1] with infinitely thick layer of fluid ( β → ∞ ). The other limiting
solution corresponding to S → 2 represents a liquid film of infinitesimal thickness ( β → 0 ). The
numerical results are obtained for 0 ≤ S ≤ 2 . Present results are compared with some of the earlier
published results in some limiting cases which are tabulated in Table 1. The effects of magnetic
parameter on various fluid dynamic quantities are shown in Fig.2 – Fig.13 for different unsteadiness
parameter.
        Fig.2 shows the variation of film thickness β with the unsteadiness parameter. It is evident
from this plot that the film thickness β decreases monotonically when S is increased from 0 to 2.
This result concurs with that observed by Wang [10]. The variation of film thickness β with respect
to the magnetic parameter Mn is projected in Fig.3 for different values of unsteadiness parameter. It
is clear from this plot that the increasing values of magnetic parameter decreases the film thickness.
The result holds for different values of unsteadiness parameter S.
        The variation of free-surface velocity f ′ ( β ) with respect to Mn is shown in Fig.4. The free
surface velocity behaves almost as a constant function of Mn as can be seen from Fig.4. The effect
of Mn on the wall shear stress parameter − f ′′ ( 0 ) is illustrated in Fig.5. Clearly, increasing values
Mn results in increasing the wall shear stress. Fig.6 demonstrates the effect of Mn on the free-
surface temperature θ ( β ) . From this plot it is evident that the free surface temperature increases
monotonically with Mn. Fig.7 highlights the effect of Mn on the dimensionless wall heat flux
−θ ′ ( 0 ) . It is found from this plot that the dimensionless wall heat flux −θ ′ ( 0 ) decreases with the
increasing values of Mn. The effect of Mn on f ′ ( β ) , − f ′′ ( 0 ) , θ ( β ) and −θ ′ ( 0 ) is observed to be
same for different values of unsteadiness parameter S.
        The effect of Mn on the axial velocity is depicted in Figs.8(a) and (b) for two different values
of S. From these plots it is clear that the increasing values of magnetic parameter decreases the axial
velocity. This is due to the fact that applied transverse magnetic field produces a drag in the form of
Lorentz force thereby decreasing the magnitude of velocity. The drop in horizontal velocity as a
consequence of increase in the strength of magnetic field is observed for both the values of S = 0.8
and S = 1.2. Figs.9 (a) and (b) depicts the effect of Mn on temperature profiles for two different
values of S. The results show that the thermal boundary layer thickness increases with the increasing
values of Mn. The increasing frictional drag due to the Lorentz force is responsible for increasing
the thermal boundary layer thickness.
        Fig.10 (a) and 10(b) demonstrate the effect of Prandtl number Pr on the temperature profiles
for two different values of unsteadiness parameter S. These plots reveals the fact that for a particular
value of Pr the temperature increases monotonically from the free surface temperature Ts to wall
velocity the T0 .


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         Fig.11 (a) and 11(b) project the effect of Eckert number Ec on the temperature profiles for
two different values of unsteadiness parameter S. The effect of viscous dissipation is to enhance the
temperature in the fluid film. i.e., increasing values of Ec contributes in thickening of thermal
boundary layer. Fig.12 (a) and Fig.12 (b) presents the effect of space dependent heat source/sink
parameter A* and Fig.13 (a) and Fig.13 (b) presents the effect of temperature dependent heat
source/sink parameter B* on the temperature profile for different values of unsteadiness parameter S
.The effect of sink parameter ( A* < 0, B* < 0) reduces the temperature in the fluid as the effect of
source parameter ( A* > 0, B* > 0) enhances the temperature. For effective cooling of the sheet, heat
sink is preferred.
       Table 1 and Table 2 give the comparison of present results with that of Wang [10]. Without
any doubt, from these tables, we can claim that our results are in excellent agreement with that of
Wang [10] under some limiting cases. Table 3 tabulates the values of surface temperature θ ( β ) for
various values of Mn, Pr, Ec, A* and B*. This table also reveals that Mn, Ec, A* and B*
proportionately increase the surface temperature whereas opposite effect is seen in case of Pr.

5. CONCLUSIONS

        A theoretical study of the boundary layer behavior in a liquid film over an unsteady
stretching sheet is carried out including the effects of a variable transverse magnetic field including
viscous dissipation and non-uniform heat source/sink. The effect of several parameters controlling
the velocity and temperature profiles are shown graphically and discussed briefly. Some of the
important findings of our analysis obtained by the graphical representation are listed below.

 1.   The effect of transverse magnetic field on a viscous incompressible electrically conducting
      fluid is to suppress the velocity field which in turn causes the enhancement of the temperature
      field.

 2.   For a wide range of Pr, the effect viscous dissipation is found to increase the dimensionless
       free-surface temperature θ ( β ) for the fluid cooling case. The impact of viscous dissipation
      on θ ( β ) diminishes in the two limiting cases: Pr → 0 and Pr → ∞ , in which situations θ ( β )
      approaches unity and zero respectively.

 3.   The viscous dissipation effect is characterized by Eckert number (Ec) in the present analysis.
      Comparing to the results without viscous dissipation, one can see that the dimensionless
      temperature will increase when the fluid is being heated (Ec>0) but decreases when the fluid
       is being cooled (Ec<0). This reveals that effect of viscous dissipation is to enhance the
      temperature in the thermal boundary layer.

 4.   The effect of non-uniform heat source/sink parameter is to generate temperature for
       increasing positive values and absorb temperature for decreasing negative values. Hence non-
      uniform heat sinks are better suited for cooling purpose.




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          TABLE 1: Comparison of values of skin friction coefficient f ′′ ( 0 ) with Mn = 0.0

                                        Wang [10]                              Present Results
             S                                                 f ′′ ( 0 )
                            β              f ′′ ( 0 )                          β           f ′′ ( 0 )
                                                                  β

            0.4         5.122490         -6.699120       -1.307785          4.981455    -1.134098
            0.6         3.131250         -3.742330       -1.195155          3.131710    -1.195128
            0.8         2.151990         -2.680940       -1.245795          2.151990    -1.245805
            1.0         1.543620         -1.972380       -1.277762          1.543617    -1.277769
            1.2         1.127780         -1.442631       -1.279177          1.127780    -1.279171
            1.4         0.821032         -1.012784       -1.233549          0.821033    -1.233545
            1.6         0.576173         -0.642397       -1.114937          0.576176    -1.114941
            1.8         0.356389         -0.309137       -0.867414          0.356390    -0.867416

                                                                                                   f ′′ ( 0 )
Note: Wang [10] has used different similarity transformation due to which the value of                        in his
                                                                                                      β
paper is the same as f ′′ ( 0 ) of our results.

    TABLE 2: Comparison of values of surface temperature θ ( β ) and wall temperature gradient
                                   −θ ′ ( 0 ) with Mn = Ec = A* = B* = 0.0
                                       Wang [10]                               Present Results
           Pr                                                 −θ ′ ( 0 )
                        θ (β )           −θ ′ ( 0 )                          θ (β )       −θ ′ ( 0 )
                                                                 β
                                           S = 0.8 and β = 2.15199

          0.01        0.960480          0.090474         0.042042           0.960438     0.042120
          0.1         0.692533          0.756162         0.351378           0.692296     0.351920
            1         0.097884          3.595790         1.670913           0.097825     1.671919
            2         0.024941          5.244150         2.436884           0.024869     2.443914
            3         0.008785          6.514440         3.027170           0.008324     3.034915

                                           S = 1.2 and β = 1.127780

          0.01        0.982331          0.037734         0.033458           0.982312     0.033515
          0.1         0.843622          0.343931         0.304962           0.843485     0.305409
            1         0.286717          1.999590         1.773032           0.286634     1.773772
            2         0.128124          2.975450         2.638324           0.128174     2.638431
            3         0.067658          3.698830         3.279744           0.067737     3.280329


                                                                                                        −θ ′ ( 0 )
Note: Wang [10] has used different similarity transformation due to which the value of                               in
                                                                                                           β
his paper is the same as −θ ′ ( 0 ) of our results.

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 TABLE 3: Values of surface temperature θ ( β ) for various values of Mn, Pr, Ec, A*, B* and S

                                                                          θ (β )
      Mn         Pr         Ec          A*          B*
                                                                S = 0.8            S = 1.2

      0.0       1.0        0.02        0.05         0.05       0.257696            0.496022
      1.0       1.0        0.02        0.05         0.05       0.420739            0.618190
      2.0       1.0        0.02        0.05         0.05       0.526782            0.692995
      5.0       1.0        0.02        0.05         0.05       0.695757            0.806962
      8.0       1.0        0.02        0.05         0.05       0.776253            0.913333

      1.0       0.01       0.02        0.05         0.05       1.030899            1.009712
      1.0       0.1        0.02        0.05         0.05       0.931433            0.959465
      1.0        1         0.02        0.05         0.05       0.420739            0.618190
      1.0        10        0.02        0.05         0.05       0.011137            0.061941
      1.0       100        0.02        0.05         0.05       0.000095            0.000238

      1.0       1.0        0.01        0.05         0.05       0.420304            0.617857
      1.0       1.0        1.0         0.05         0.05       0.463423            0.650865
      1.0       1.0        2.0         0.05         0.05       0.506978            0.684207
      1.0       1.0        5.0         0.05         0.05       0.637642            0.784232

      1.0       1.0        0.02        0.05         0.05       0.227566            0.423871
      1.0       1.0        0.02        0.05         0.05       0.420739            0.618190
      1.0       1.0        0.02        0.05         0.05     0.715871               0.838324
      1.0       1.0        0.02        0.05         0.05       0.826899            0.906104

      1.0       1.0        0.02        -0.4         0.05       0.379098            0.586395
      1.0       1.0        0.02         0.0         0.05       0.416112            0.614657
      1.0       1.0        0.02         0.4         0.05       0.453127            0.642920

      1.0       1.0        0.02        0.05         -0.4       0.353675            0.578066
      1.0       1.0        0.02        0.05         0.0        0.412373            0.613518
      1.0       1.0        0.02        0.05         0.4        0.487372            0.652540




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                                                                                                              y=h
                                                x
                                                                             u
                                         Slit                                                                         h(t)
                                                              y
                                                                                                                                              Forc
                                                                        Ts                                    y=0



                                   Fig.1 Schematic representation of a liquid film on an elastic sheet

         50
                                                                                                    2.0



         40
                                                                                                    1.6



         30
                                                                                                    1.2
                                                                                            β                                  S = 0.8
     β

         20                                                                                         0.8
                                                                                                                       S = 1.2

         10                                                                                         0.4




               0                                                                                    0.0
                   0.0             0.5              1.0           1.5         2.0                         0                2              4             6              8

                                                    S                                                                                    Mn
                   Fig.2 Variation of film thickness β with unsteadiness                                  Fig.3 Variation of film thickeness β with magnetic
                         parameter S with Mn = 0.0                                                              parameter Mn




                   0.5                                                                                  3.5


                                                                                                        3.0
                   0.4                           S = 1.2
                                                                                                        2.5                              S = 0.8

                   0.3                                                                                                                        S = 1.2
                                                                                                        2.0
                                                                                            -f '' (0)
     f ' (β)




                                                                                                        1.5
                   0.2                          S = 0.8
                                                                                                        1.0

                   0.1
                                                                                                        0.5


                   0.0                                                                                  0.0
                         0               2                4         6             8                           0            2              4             6          8

                                                  Mn                                                                                    Mn
                         Fig.4 Variation of free-surface velocity f ' (β ) with                               Fig.5 Variation of wall shear stress parameter -f '' (0)
                               magnetic parameter Mn                                                                with Magnetic parameter Mn




                                                                                      396
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME



            1.0                                                                                             1.2




            0.8                                  S = 1.2
                                                                                                            1.0



            0.6
                                                                                                                                                                    S = 0.8
  θ (η)




                                                                                                            0.8




                                                                                                 -θ '(0)
                                        S = 0.8
            0.4
                                                                                                            0.6
                                                                                                                                                             S = 1.2


            0.2

                                                                                                            0.4

            0.0
                  0                 2                4             6               8                              0                      2               4                6             8
                                                     η                                                                                     Mn
                      Fig.6 Variation of free-surface temperature θ(β)                                           Fig. 7 Dimensionless emperature gradien -θ '(η) at the sheet vs
                            with the Magnetic parameter Mn                                                             Magnetic parameter Mn for S = 0.8 and S = 1.2



      2.5

                                                                    β = 2.151990
                                                                                                           1.2
                                                                                                                                                                              β = 1.127780
      2.0

                                                                                                           1.0
                                                                   β = 1.616880                                                                                                β = 0.903878
      1.5
                                                                    β = 1.350880                           0.8                                                                β = 0.775795
  η




                                                                                                 η




      1.0                                                           β = 0.979193                           0.6                                                                β = 0.579900
                                                                    β = 0.806512                                                                                               β = 0.483049
                                                                                                           0.4
      0.5

                                                                                                           0.2
                      Mn = 0, 1, 2, 5, 8                                                                                                   M = 0, 1, 2, 5, 8
      0.0
            0.0              0.2           0.4             0.6         0.8        1.0                      0.0
                                                  f '(η)                                                         0.0               0.2            0.4              0.6         0.8           1.0
                  Fig. 8(a) Variation in the velocity profile f ' (η) for different                                                                      f ' (η)
                        values of magnetic parameer Mn with S = 0.8                                               Fig. 8(b) Variation in the velocity profile f ' (η) for different
                                                                                                                        values of magnetic parameer Mn with S = 1.2




          2.5
                                                                                                                 1.2
                                                                                                                                                                              β = 1.127780
                                                                    β = 2.151990
          2.0                                                                                                    1.0
                                                                                                                                                                              β = 0.903878
                                                                    β = 1.616880
                                                                                                                 0.8                                                          β = 0.775795
          1.5
                                                                    β = 1.350880
                                                                                                      η
  η




                                                                                                                 0.6                                                          β = 0.579900
          1.0                                                       β = 0.979193                                                                                              β = 0.483049
                                                                    β = 0.806512                                 0.4


          0.5
                                                                                                                 0.2
                                                                                                                                                   M = 0, 1, 2, 5, 8
                              M = 0, 1, 2, 5, 8
                                                                                                                 0.0
          0.0
                                                                                                                       0.0           0.2           0.4             0.6        0.8        1.0
                0.0           0.2          0.4             0.6         0.8        1.0
                                                                                                                                                        θ (η)
                                                  θ (η)
                                                                                                                             Fig.9(b) Variation on the temperature profile θ (η) for different
                      Fig.9(a) Variation oin the temperature profile θ (η) for different
                                                                                                                                   values of magnetic parameter Mn with S = 1.2
                      values of magnetic parameter Mn with S = 0.8




                                                                                           397
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME

              Mn = 1, Ec = 0.02, A* = B* = 0.05                                                                            Mn=1, Pr = 1, Ec = 0.02, A* = B* = 0.05
                                                                                                                1.0

                                                                                 β = 1.61688                                                                                          β = 0.903878
      1.6

                                                                                 Pr=0.1                         0.8                                                                         Pr = 0.1


      1.2                                           Pr=1                                                                                                                   Pr = 1
                                                                                                                0.6

                         Pr=5                                                                                                                    Pr = 5




                                                                                                           η
  η




      0.8
                                                                                                                0.4                      Pr = 10
                      Pr=10

                                                                                                                0.2
                                                                                                                               Pr = 100
      0.4

                     Pr=100

                                                                                                                0.0
      0.0                                                                                                              0.0               0.2               0.4            0.6           0.8            1.0
            0.0            0.2             0.4               0.6                0.8          1.0                                                                 θ (η)
                                                 θ(η)
             Fig.10(a) Variation of the temperature profile θ (η) for different                                              Fig.10(b) Variation in he temperaure profile θ (η) for different
                                                                                                                                   values of Prandtl number Pr with S = 1.2
                   values of Prandtl number Pr with S = 0.8




             Mn=1, Pr = 1, A* = B* = 0.05                                                                             Mn = 1, Pr = 1, A* = B* = 0.05
                                                                                                               1.0
                                                                               β = 1.61688                                                                                       β = 0.903878
      1.6

                                                                                                               0.8


      1.2
                                                                                                               0.6
                                                                                                           η




                                                                                                                                               Ec = 0.01, 1, 2, 5
  η




      0.8
                                                                                                               0.4
                       Ec = 0.01, 1, 2, 5

      0.4
                                                                                                               0.2




      0.0                                                                                                      0.0
            0.0          0.2         0.4             0.6                 0.8          1.0                            0.0           0.2               0.4            0.6         0.8           1.0
                                           θ( η )                                                                                                           θ (η)
                  Fig.11(a) Variation in the temperature profile θ (η) for different                                 Fig.11(b) Variation in the temperature profile θ (η) for different
                        values of Eckert number Ec with S = 0.8                                                            values of Eckert number Ec with S = 1.2




                  Mn = 1, Pr = 1.0, Ec = 0.02, B* = 0.5                                                                    Mn=1, Pr = 1, Ec = 0.02, B* = 0.05
                                                                                                                1.0

                                                                                        β 1.61688                                                                                      β = 0.903878
       1.6

                                                                                                                0.8


       1.2
                                                                                                                0.6
  η




                                                                                                           η




       0.8                                                                                                                     A* = -0.4, -0.2, 0, 0.2, 0.4
                   A* = -0.4, -0.2, 0, 0.2, 0.4                                                                 0.4



       0.4
                                                                                                                0.2




       0.0                                                                                                      0.0
             0.0               0.2            0.4                  0.6                0.8          1.0                0.2                      0.4                  0.6               0.8               1.0
                                                        θ ( η)                                                                                              θ (η)
                  Fig 12(a). Variation of temperature profile θ (η)                                                          Fig 12(b). Variation of temperature profile θ (η)
                     for different values of space dependent heat                                                               for different values of space dependent heat
                                    *                                                                                                          *
                     source/sink A with S = 0.8                                                                                 source/sink A with S = 1.2




                                                                                                     398
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME

             Mn = 1, Pr = 1, Ec = 0.02, A* = 0.05                                         Mn = 1, Pr = 1, Ec = 0.02, A* = 0.05
                                                                                   1.0
                                                         β = 1.61688                                                                  β = 0.903878
      1.6

                                                                                   0.8


      1.2
                                                                                   0.6
  η




                                                                               η
      0.8                                                                                      B* = -0.4, -0.2, 0, 0.2, 0.4
              B* = -0.4, -0.2, 0, 0.2, 0.4                                         0.4



      0.4
                                                                                   0.2




      0.0                                                                          0.0
            0.0         0.2         0.4            0.6   0.8       1.0                   0.2            0.4            0.6          0.8            1.0
                                          θ (η )                                                                    θ (η)
       Fig 13 (a). Variation of the temperature profile θ(η)                               Fig 13 (b). Variation of the temperature profile θ(η)
       for different values of temperature dependent heat                                  for different values of temperature dependent heat
                      *                                                                                   *
       source/sink B with S = 0.8                                                          source/sink B with S = 1.2




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