A hybrid computational and analytical model of irrigation drip emitters

Abstract

This thesis details a hybrid computational and analytical model to predict the performance of inline pressure-compensating (PC) drip emitters. A verified CFD model is used to predict flow behavior through tortuous paths. A method of extracting a pressure scaling parameter from the CFD results for use in an analytical model is presented. Analytical expressions that describe the bending of asymmetric rectangular membranes in inline drip emitters are detailed. These expressions are combined with finite element analysis (FEA) describing the shearing behavior of the membrane to model the total flow resistance through the emitter. Analytical expressions that describe the fluid mechanics of duct and turbulent flows are used to predict the net flow rate out of the emitter. The final model is verified for three distinct emitter geometries. The hybrid model presented in this paper has wide applicability - it can be applied to asymmetrical emitter geometries that have tortuous paths and other complex flow geometries. The hybrid model benefits from the accuracy of computational modeling for complex flows and contact interactions, and the processing speed of analytical models. Because of its accuracy and speed, the model can be used reliably as a design tool for inline PC emitters.