Page 251 - Bird R.B. Transport phenomena

§8.1 Examples of the Behavior of Polymeric Liquids 235
Fig. 8.1=5. Flow down a tilted semicylindri-
cal trough. The convexity of the polymeric
liquid surface is somewhat exaggerated here.

dial and axial secondary flow, but the latter goes in a direction opposite to that seen in
the Newtonian fluid. 5
In another experiment we can let a liquid flow down a tilted, semi-cylindrical
trough as shown in Fig. 8.1-5. If the fluid is Newtonian, the liquid surface is flat, except
for the meniscus effects at the outer edges. For most polymeric liquids, however, the liquid
surface is found to be slightly convex. The effect is small but reproducible. 6

Some Other Experiments
The operation of a simple siphon is familiar to everyone. We know from experience that,
if the fluid is Newtonian, the removal of the siphon tube from the liquid means that the
siphoning action ceases. However, as may be seen in Fig. 8.1-6, for polymeric liquids the
siphoning can continue even when the siphon is lifted several centimeters above the liq-
uid surface. This is called the tubeless siphon effect. One can also just lift some of the fluid
up over the edge of the beaker and then the fluid will flow upward along the inside of
the beaker and then down the outside until the beaker is nearly empty/
In another experiment a long cylindrical rod, with its axis in the z direction, is made
to oscillate back and forth in the x direction with the axis parallel to the z axis (see Fig.

Fig. 8.1-6. Siphoning continues to occur
when the tube is raised above the surface
of a polymeric liquid, but not so for a
Newtonian liquid. Note the swelling of
(?) "Extrudate the polymeric liquid as it leaves the
swell" siphon tube.

5
С. Т. Hill, J. D. Huppler, and R. B. Bird, Chem. Eng. Sci. 21, 815-817 (1966); С. Т. Hill, Trans. Soc.
Rheol., 16, 213-245 (1972). Theoretical analyses have been given by J. M. Kramer and M. W. Johnson, Jr.,
Trans. Soc. Rheol. 16,197-212 (1972), and by J. P. Nirschl and W. E. Stewart, /. Non-Newtonian Fluid Mech.,
16, 233-250 (1984).
6
This experiment was first done by R. I. Tanner, Trans. Soc. Rheol., 14,483-507 (1970), prompted by
a suggestion by A. S. Wineman and A. C. Pipkin, Ada Mech. 2,104-115 (1966). See also R. I. Tanner,
Engineering Rheology, Oxford University Press (1985), 102-105.
7
D. F. James, Nature, 212, 754-756 (1966).