| Author(s) | A.A. Alazba |
| Affiliation | Agricultural Engineering Department, College of Agriculture and Food Sciences, King Saud University, P.O. Box 2460, Riyadh 11451, Saudi Arabia |
| Title | Calculating F Factor for Center-pivots Using Simplified Formula and Modified Christiansen Equation |
| Source | Journal of King Saud University. Agricultural Sciences. Volume 17, No 2. (2005/1425) |
| Abstract | A single-accurate exponential equation is presented to estimate the friction correction factor for center-pivot systems. The proposed equation is simpler than and well agreed with the previously developed equations of the correction friction factors. For a large number of outlets, two simplified forms have also been presented. The presented equation and its subsequently derived forms are uniquely functions of the number of outlets N and the flow exponent m of the used friction formula. Also, the Christiansen friction correction factor, originally devised for systems where discharge decreases linearly with distance, was adapted to simply and accurately estimate the friction correction factor and, consequently, to facilitate the head loss calculation in the center-pivot laterals. The developed formulas of the friction correction factors were compared to the previously proposed equations. The results showed well agreement between the present and the previous equations for determining the friction correction factors for center-pivots laterals. Numerically documented and field examples have been used to test the presented equations. The examples outputs revealed that the equations can be used to determine the friction correction factors for a pipe of non-uniformly discharging outlets with insignificant errors. For practical number of outlets for center-pivot laterals, the errors were mostly in the vicinity of ± 2 %. |
