ɧe = ζev12/2g,
(1)
if ζe is put for the expression in brackets.
| ω1/ω0 = | 1.1 | 1.2 | 1.5 | 1.7 | 1.8 | 1.9 | 2.0 | 2.5 | 3.0 | 3.5 | 4.0 | 5.0 | 6.0 | 7.0 | 8.0 |
| d1/d0 = | 1.05 | 1.10 | 1.22 | 1.30 | 1.34 | 1.38 | 1.41 | 1.58 | 1.73 | 1.87 | 2.00 | 2.24 | 2.45 | 2.65 | 2.83 |
| ζe = | .01 | .04 | .25 | .49 | .64 | .81 | 1.00 | 2.25 | 4.00 | 6.25 | 9.00 | 16.00 | 25.00 | 36.0 | 49.0 |
| Fig. 88. | Fig. 89. |
Abrupt Contraction of Section.—When water passes from a larger to a smaller section, as in figs. 88, 89, a contraction is formed, and the contracted stream abruptly expands to fill the section of the pipe. Let ω be the section and v the velocity of the stream at bb. At aa the section will be ccω, and the velocity (ω/ccω) v = v/c1, where cc is the coefficient of contraction. Then the head lost is
ɧm = (v/cc − v)2 / 2g = (1/cc − 1)2 v2/2g;
and, if cc is taken 0.64,
ɧm = 0.316 v2/2g.
(2)