| Summary: | Abstract Drip irrigation has the potential to help farmers increase crop production with lower on-farm water consumption than flood or sprinkler irrigation; yet, its high costs keep it out of reach for many smallholder farmers, who make up about 20 $$\%$$ % of the world's population. Pressure-compensating (PC) drip emitters enable uniform water delivery to all crops in a field by regulating the emitter flow rate, but typically require high pumping pressures, contributing to high capital and operating costs for the pump and power system. Redesigning PC emitters for lower pressure operation could enable more energy-efficient and affordable drip systems. However, the current lack of published design theory for PC emitters hinders the development of emitters with desired hydraulic performance. To address this gap, we present an analytical, parametric model for the hydraulic behavior (i.e., the flow rate versus pressure curve) of inline PC emitters before the flow-regulating regime. We combine this model with a validated prototyping method to demonstrate its utility in the design of PC emitters with target activation pressures and flow rates, and demonstrate a sample design that achieves 38 $$\%$$ % lower activation pressure than commercial emitters with similar flow rates. The proposed model sheds light on the parametric relationships between PC emitter geometry and performance. It may inform R&D efforts in the irrigation industry and lead to improved emitter designs with low operating pressures, helping reduce drip system costs and increase access to drip irrigation among smallholder farmers.
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