Hydrodynamical changes due to polymer migration in very dilute solutions |
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Authors: | A Dutta R A Mashelkar |
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Institution: | (1) Polymer Engineering Group, Chemical Engineering Division, National Chemical Laboratory, 411008 Pune, India |
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Abstract: | The slip hypothesis, based on thermodynamical arguments, has been extended to obtain the flow characteristics of polymer solutions flowing in a nonhomogeneous flow field. An asymptotic analysis, valid for both channel and falling film flows, is presented that predicts the flow enhancement due to polymer migration. Concentration-viscosity coupling is shown to be a critical factor in the hydrodynamic analysis. The analysis, which essentially provides an upper bound on flow enhancement, explicitly accounts for the influence of wall shear stress, initial polymer concentration etc. A comparison with the pertinent experimental data shows reasonable agreement.
c
concentration
-
c
0
concentration in shear-free region
-
c
i
initial concentration
-
d
rate of deformation tensor
-
g
acceleration due to gravity
-
g
1
function defined in eq. 13] or 15]
-
g
2
function defined in eq. 18] or 20]
-
H
half-channel thickness or film thickness
-
K
gas law constant
-
L
length of the channel or film
-
q
flow rate per unit width
-
q
*
normalized flow rate
-
T
temperature
-
v
velocity
-
V
mean velocity
-
y
transverse distance
-
y
c
location of solvent layer
-
w
/µ
s
-
w
/c
0
KT
-
/ t
convected derivative
-
dimensionless cenentration,c/c
0
-
c
dimensionless interface concentration
-
w
dimensionless wall concentration
-
relaxation time
-
µ
eff
effective viscosity
-
µ
s
solvent viscosity
-
dimensionless transverse distance,y/H
-
c
dimensionless interface location
-
density
-
stress tensor
-
w
wall shear stress
-
c
i
KT/
w
- ns
no slip
NCL-Communication No. 3155 |
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Keywords: | Slip polymer solutions non-uniform flow field |
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