24

FLUIDITY AND PLASTICITY

TABLE VIII.—VISCOSITY OF WATER CALCULATED FROM POISEUILLE'S

EXPERIMENTS ' WITH TUBE Av
For dimensions cf. Appendix D, Table I, p. 331

Time
TjpEq. (5)
-n' Eq. (8), m = 1.00

3,829
0.01383
0.01363

1,924
0.01404
0.01363

994
0.01442
0.01363

682
0.01479
0.01364

537
0.01512
0.01366

291
0.01651
0.01382

165
0.01863
0.01388

The values of 77 vary but little around the mean 0.01329, while
the values of rip show a regular progression, thus demonstrating
the importance of the kinetic energy correction. The first three
values of tf in Table VIII are constant and equal to 0.01363.
The last four values show a steady increase which may be due to
turbulent flow at such high velocities. From i\ and V, which are
notably different in value, the corrected viscosity T\C as well as the
value of A may be obtained by the use of Eq. (11). We get
yc = 0.01303 and A = 0.041 cm. The mean diameter of these
tubes was 0.01417 cm hence, the fictitious elongation of the tube

is a little less than three times the diameter ( «p = 2.868) •

Couette also obtained the corrected viscosity directly by
experiment, in a very ingenious manner. He employed two
capillaries simultaneously, which had the same diameter but
different lengths. The arrangement of his apparatus is shown in
Fig. 4, where TI and T2 are the two capillaries connecting three
reservoirs M, N, and P. The pressure in each reservoir is
measured on the differential manometer H. Since the volume of
efflux through both capillaries is the same and may be calculated
from the increase in weight of the liquid in the receiving flask D,
we obtain from Eqs. (7) and (9) the relation

or

7

7

+ A) 8Vrjc(h -• A)

irgR*t pi —
*