Abstract
In this paper, the authors investigated the hydraulic coefficients based on the field test for a recently developed rigid PE pipe of large diameter, to provide a technological basis for rationalizing the pipe distribution system for sprinkler irrigation.
The results obtained are summarized as follows:
(1) Measured values of the coefficients in hydraulic flow formulas were: f=0.011-0.012, C=170-177, for the 600 mm straight pipe, and f=0.018-0.019, C=130-132, Ks=0.33-0.34, n=0.011 for the inverted siphon, respectively. The cause of increased resistance against flow for the inverted siphon is regarded due mainly to the effect of air in the pipe.
(2) Judging from the coefficients and Reynolds numbers forthe straight pipe and inverted siphon, the Darcy-Weisbach formula can be applied for the former pipe and the Scobey formula for the latter.
(3) Diagrams (Fig.3, 4) were prepared for the purpose of estimating the coefficients for a pipe of the same kind of any given diameter from the coefficients measured within the region of diameter where Hazen-Williams formula or Scobey formula is applicable respectively.
(4) In using a certain constant in place of correct coefficient in a restricted range of dismeters it is preferable to adopt two respective constants for two sub-divided range of diameter, e. g. by dividing a total range of 65-1, 500 mm at 300 mm, rather than to use single constant for the whole range.
(5) Both the values of C determined with the Matsuda's slide-rule for hydraulic use and of Ks from the nrenared nnmnaranh (Fig.5) acrreed accurately with correspondina logarithmic calculations.
