Assessing A Computational Fluid Dynamics Technique (CFD) To Evaluate Pressure Losses In Co-Extruded Drip Laterals

Abstract

The hydraulic design of drip laterals or irrigation units needs the estimation of head losses along the pipes, depending from both the friction and the local losses due to the emitter connections, whose importance has been recently emphasized. Since each emitter local loss depends on the shape and dimensions of the protrusion, due to the morphological variability of the commercially available emitters, experimental investigations are necessary in order to evaluate local losses. To avoid the expensive and time consuming experiments local losses in drip laterals can be evaluated by mean of empirical procedures, as a function of an obstruction index, evaluable by considering the emitter’s and pipe’s dimensions. Local losses can also be computed by analyzing the turbulence produced around the emitter (analytical approach). This latter possibility has been recently offered by the Computational Fluid Dynamics (CFD) models. FLUENT software can be considered a powerful tool for evaluating local losses in drip irrigation laterals, after the necessary validation, that must be carried out by means of experimental data. The main objective of this paper is to assess a CFD technique to evaluate friction and local losses in laterals with in-line co-extruded emitters. The turbulence was initially analyzed in order to establish the flow resistance law parameters and to evaluate accurately the friction losses. Secondly the possibility to use CFD to predict local losses in drip irrigation laterals, where coextruded emitters are installed, was investigated. The research allowed to verify the feasibility of the CFD technique to evaluate friction and local losses in drip laterals and for Reynolds numbers in the range of turbulent flow