In this paper, the authors measured head losses of widely used rigid PVC pipes in actual system, for the purpose of obtaining basic data for rationalizing the pipe distribution system for sprinkler irrigation, and investigated about the various hydraulic coefficients of pipes for design use, applicable formulas and so on.
The results obtained are summarized as follows:
(1) Actual values of the coefficients in hydraulic flow formulas for the 30, 50, 100 and 125 mm sprinkler and distribution pipes were respectively K_s= 0.38-0.32, C= 130-140, f= 0.026-0.020 and n= 0.009-0.008.These coefficients were found to vary with pipe sizes.
(2) There was large difference between the coefficients of sprinkler and distribution pipes and transmission pipes. Therefore the Scobey formula is applicable to the former pipes (especially in sloped land) and the Manning formula to the latter, judging from the coefficients and Reynolds numbers.
(3) Adequate design values of K_s are 0.38 for 20-30 mm, 0.36 for 35-65mm, 0.34 for 75-100mm and 0.32 for 125-150mm sprinkler and distribution pipes.
(4) Reliability of the above coefficients was verified by applying these coefficients to actual calculation, and by comparing measured and calculated pressures in sprinkler heads of two different pipe-line arrangements.
(5) In using a certain constant coefficient in a restricted range of diameters for pipes of the same material, it is reasonable to select the coefficient for pipe diameter of the longest line.