Abstract
In this paper, the slow steady motion of a second order thermo-viscous fluid between two parallel plates is examined. The closed form
solutions of the velocity and temperature distributions are obtained when thermo-stress coefficient is far less compared to strain
thermal conductivity coefficient and coefficient of cross viscosity for the following two cases: (i) when the upper plate is in relative
motion and (ii) when the upper plate is thermally insulated. The heat transfer coefficient on the upper plate , The mean Bulk
temperature and the transverse force perpendicular to the flow direction are also calculated. It is observed that forces are generated
in transverse directions which are special feature of these types of fluids. The effect of various flow parameters on the flow field have
been discussed with the help of graphical illustrations.
Keywords: Thermo-viscous fluids, Strain thermal conductivity coefficient and Thermo stress Coefficient.
2. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
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Volume: 02 Issue: 11 | Nov-2013, Available @ http://www.ijret.org 295
ο½ο§ Thermal energy source per unit mass
and
th
i iq ο½ Component of heat flux bivector = 2/jkijk hο
Solving a specific boundary value problem would mean,
finding the solution of these equations with appropriate
boundary conditions such as the no slip condition (i.e. the
velocity of fluid relative to the boundary is zero) and the
prescription of the wall temperature. The later condition may
be replaced by the prescription of heat flux on the boundary.
2. MATHEMATICAL FORMULATION AND
SOLUTION OF THE PROBLEM
With reference to the Cartesian coordinates system O(x, y, z)
with origin on the lower plate, the X-axis in the direction of
flow. The flow is characterized by the velocity field
[π’(π¦), 0, 0 ] and temperature by π(y).
Y π’ = π’0 , π = π1
Temperature )(yο±
Pressure Gradient h Fluid Velocity π’(π¦)
π’ = 0 π = π0
X
Fig 1: Flow Configuration
In the absence of any external force in the direction of flow,
the equations of motion reduces to
0 = -
ππ
ππ₯
+ π
π2 π’
ππ¦2 - πΌ6
ππ
ππ₯
π2 π
ππ¦2 (1)
πc
π
ππ¦
ππ’
ππ¦
2
+ πFy = 0 (2)
πΌ8
π
ππ¦
ππ
ππ¦
ππ’
ππ¦
+ πFz = 0 (3)
In the absence of any heat source, the energy equation reduces
to
πc u
ππ
ππ₯
=π
ππ’
ππ¦
2
- πΌ6
ππ
ππ₯
ππ’
ππ¦
ππ
ππ¦
+k
π2 π
ππ¦2 + π½3
ππ
ππ₯
π2 π’
ππ¦2
(4)
together with the boundary conditions:
π’(0) = 0 , π(0) = π0 (5)
π’ β = π’0 , π β = π1 (6)
Introducing the following non-dimensional quantities,
π¦ = βπ , π’ = (π/πβ)π, π =
πβπ0
π1βπ0
,
ππ
ππ₯
=
π1βπ0
β
π2
and -
ππ
ππ₯
=
π2
πβ3 π1
The equation (1) and (4) can be reduced to
0 =π1 +
π2 π
ππ2 -π΄6 π2
π2 π
ππ2 (7)
and
ππ2 = π΄1
dU
dY
2
β π΄6 πΆ2
ππ
ππ
ππ
ππ
+
1
π π
π2 π
ππ2 + π΅3 πΆ2
π2 π
ππ2 (8)
With
ππ =
ππ
π
(Prandtle number), S=
πβ π£0
π
, B3 =
π½3
πβ2 π
,
A1 =
π2
πβ2 π π1βπ0
and A6 =
πΌ6 π1βπ0
2
π2
where
πΆ1 is Non-Dimensional constant pressure gradient and
πΆ2 is Non-Dimensional constant temperature gradient.
The boundary conditions are U(0) = 0 , U(1) = π0
T(0) = 0 , T(1) = 1
3. CASE-I: WHEN UPPER PLATE IS IN
RELATIVE MOTION
Assuming that the thermo β stress coefficient πΌ6 is far less
when compared to strain thermal conductivity coefficient π½3
and coefficient of cross viscosity πc.
The equations (7) and (8) reduces to
0 = π1 +
π2 π
ππ2 (9)
ππ2 = π΄1
dU
dY
2
+
1
π π
π2 π
π π2 +π΅3 πΆ2
π2 π
ππ2 (10)
The boundary conditions reduces to
U(0) = 0 , T(0) = 0 (11)
U(1) = π0 , T(1) = 1 (12)
3. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
Volume: 02 Issue: 11 | Nov-2013, Available @ http://www.ijret.org 296
i.e. the upper plate is moving with a given velocity and the
two plates are maintained at different temperatures.
The equations (9) and (10) together with the boundary
conditions (11) and (12) yield the velocity
π π =
πΆ1
2
π 1 β π + π0 π
And the temperature
π π = π + π΄1 ππ
πΆ1
2
24
2π2
β 2π + 1 +
π0
2
2
β
π0πΆ16 2πβ1π1β π+πΆ2ππ πΆ124π2β πβ1β
π06 1+πβ π΅3πΆ22 π 1β π
The heat transfer coefficient i.e. Nussult number βNuβ on the
upper plate is
Nu=
ππ
ππ π=1
= β
π΄1 ππ
24
πΆ1 β 2π0
2
+ 8 π0
2
+
πΆ2 ππ
24
πΆ1 + 8π0 + 12π΅3 πΆ2 + 1
Which depends on constant pressure gradientπΆ1, the relative
velocity of upper plate π0 and π΅3 the strain thermal
conductivity coefficient, constant temperature gradient πΆ2 and
the prandtle number ππ.
Also the mean Bulk temperature =
ππ ππ
1
0
π ππ
1
0
=
π0
1
3 + π΄1 ππ
πΆ1
2
480 +
π0
2
24 β
π0 πΆ1
360
βπΆ2 ππ
πΆ1
240 β
π0
45 +
π΅3 πΆ2
24
+πΆ1
1
24 + π΄1 ππ
πΆ1
2
2520 +
π0
2
120 β
π0 πΆ1
360
βπΆ2 ππ
17πΆ1
20160 β
π0
240 +
π΅3 πΆ2
240
π0 +
πΆ1
6
The forces generated in transverse direction are
ππΉπ¦ = 2π π
π2
π2β4 π0 +
πΆ1
2
2π β 1 πΆ1
ππΉπ§ =
πΌ8 π π1βπ0
β4 π
=
π1
1 + π΄1 ππ
πΆ1
2
6
1 + 6π2
β 8π3
+
π0 πΆ1
3
2 β 9π
+9π2
πΆ2 ππ
β
πΆ1
24
1 + 6π β 24π2
+ 16π3
+
π0
6
1 + 3π β 9π2
β
π΅3 πΆ2
2
β1 + π + 2π2
βπ0 ππ
π΄1
πΆ1
2
4
1 β 4π + 4π2
β π0
2
β3π0 πΆ1 β1 + 2π
+πΆ2
πΆ1
2
π β π2
β π0 π
+π΅3 πΆ2 π
It is observed that these forces generated in transverse
directions depends on the cross viscosity π π and on πΌ8 the
thermo stress viscosity.
4. CASE-II: WHEN UPPER PLATE IS
INSULATED
Y π’ = π’0 ,
ππ
ππ¦
= 0
Temperature )(yο±
Pressure Gradient h Fluid Velocity π’(π¦)
π’ = 0 , π = π0
X
Fig.2: Flow Configuration
The equations of motion and energy reduces to
0 = π1 +
π2 π
ππ2 -π΄6 π2
π2 π
ππ2 (13)
ππ2 =A1
dU
dY
2
β A6C2
ππ
ππ
ππ
ππ
+
1
π π
π2 π
ππ2 + B3C2
π2 π
ππ2 (14)
Together with the boundary conditions:
U(0) = 0 , T(0) = 0 (15)
U(1) = π0 ,
ππ
ππ π=1
= 0 (16)
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__________________________________________________________________________________________
Volume: 02 Issue: 11 | Nov-2013, Available @ http://www.ijret.org 297
The velocity field is same as in Newtonian case and is given
by
π π =
πΆ1
2
π 1 β π + π0 π
And the temperature field is given by
π π = ππ πΆ2
πΆ1
24
β π3
+ 2π2
β 2 +
π0
6
π2
β 3
π
+π΄1 ππ
πΆ1
2
24
2 β 3π + 4π2
β 2π3
β
πΆ1 π0
6
3 β
2ππ+π022(2β π)π+ π΅3πΆ1πΆ2ππ2 (πβ2)π
The forces generated in transverse direction are
ππΉπ¦ = 2π π
π2
π2β4
π0 +
πΆ1
2
2π β 1 πΆ1
ππΉπ§=
πΆ1 πΌ8 ππ0
ππ πΆ2
π1
12
1 β 3π + 6π2
β 4π3
+
π0
2
1 + π β 3π2
+ππ A1
πΆ1
2
24
32π3
β 48π2
+ 24π β 5
βπΆ1 π0 β5π2
+ 5π β 1 +
π0
2
2
4π β 3
+
ππ π΅3 πΆ1 πΆ2
2
3 β 4π
+ π0
ππ πΆ2
π1
12
βπ2
+ π + π0 π
βππ A1
πΆ1
2
24
4π2
β 4π + 1 + πΆ1 π0 1 β 2π + π0
2
+ ππ π΅3 πΆ1 πΆ2
Which depends on πΌ8 , π΅3 , pressure gradient, given velocity
of upper plate and the constant temperature gradient.
5. RESULTS AND DISCUSSION
Numerical estimates of the velocity and temperature fields
was carried for different values of π0=(0 ,1) by taking
πΆ1 = 1, A1 = 1, ππ = 1 and these are illustrated graphically.
When the upper plate is fixed, thermally insulated or not, the
velocity is parabolic in general. When the upper plate is in
relative motion with a given velocity, the velocity of the fluid
is steadily increased so as to attain the velocity of the upper
plate, this is observed from the Fig 3.
Fig 3: Velocity Profile
The temperature distributions for different values of B3 are
illustrated graphically in Fig. 4, 5 and 6
When the upper plate is not thermally insulated temperature
increases gradually to attain the temperature of the upper plate
and when it is thermally insulated temperature decreases.
Fig 4: Temperature Profile
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
U(Y)
Y
VELOCITY PROFILE
UO=0
U0=1
-0.5 0 0.5 1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
T(Y)
Y
TEMPERATURE PROFILE
UO=0,B3=1
no insulation
with insulation
5. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
Volume: 02 Issue: 11 | Nov-2013, Available @ http://www.ijret.org 298
Fig.5: Temperature Profile
Fig.6: Temperature Profile
When the upper plate is in relative motion, temperature
distributions for different values of B3 are illustrated
graphically in the figures 7, 8 and 9.
When the upper plate is not thermally insulated temperature
increases gradually to attain the temperature of the upper plate
and when it is thermally insulated temperature decreases.
Fig.7: Temperature Profile
Fig 8: Temperature Profile
Fig.9: Temperature Profile
-1.5 -1 -0.5 0 0.5 1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
T(Y)
Y
TEMPERATURE PROFILE
UO=0,B3=3
no insulation
with insulation
-2.5 -2 -1.5 -1 -0.5 0 0.5 1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
T(Y)
Y
TEMPERATURE PROFILE
UO=0,B3=5
no insulation
with insulation
-0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
T(Y)
Y
TEMPERATURE PROFILE
UO=1,B3=1
no insulation
with insulation
-1.5 -1 -0.5 0 0.5 1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
T(Y)
Y
TEMPERATURE PROFILE
UO=1,B3=3
no insulation
with insulation
-2.5 -2 -1.5 -1 -0.5 0 0.5 1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
TEMPERATURE PROFILE
UO=1,B3=5
T(Y)
Y
no insulation
with insulation
6. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
Volume: 02 Issue: 11 | Nov-2013, Available @ http://www.ijret.org 299
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