Tapered Drip Laterals and Manifolds Laid on Flat Fields: Analytical Solutions and Energy-Saving Potential

Abstract

A new analytical procedure is developed to design microirrigation units of rectangular shape with tapered laterals and manifolds laid on flat fields. The methodology relies on a normalizing pressure heads approach based on the pressure head tolerances concept to assure limited emitter flow rate variability across all emitters. The results indicated that tapered laterals primarily enhance energy saving and efficiency in drip irrigation systems. Moreover, the proposed procedure included new relationships for tapered laterals and manifolds helping identify commercial characteristics of emitters and pipe diameters. The validation of the proposed analytical procedure was performed by the comparison of results with the precise stepwise solution conducted for #1,000 simulations. Since the procedure had been based on the assumption of uniform emitter flow rates, no errors occurred when the exponent x of the emitter flow relation was set equal to zero. While for nonpressure compensating emitters (x>0) slight relative errors in inlet pressure head (Res), occur, laying in a very limited range, from -1.2% to 0.8%, and reaching the maximum values for the fully laminar flow condition (x=1). A numerical application was performed to illustrate the reliability of the suggested design procedure, also illustrating that an energy-saving ES=55.6% was achieved. Results also illustrated that much higher ESs can be achieved for different geometric and hydraulic characteristics of the tapered units. The proposed methodology could serve as a foundational framework for saving energy in drip irrigation systems, and for analyzing the effects of tapered laterals and manifolds on the design variables.