Effects of Flow Path Geometrical Parameters on the Hydraulic Performance of Variable Flow Emitters at the Conventional Water Supply Stage

Ni Gao, Yan Mo (), Jiandong Wang, Luhua Yang () and Shihong Gong
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Ni Gao: College of Water Conservancy Engineering, Tianjin Agricultural University, Tianjin 300384, China
Yan Mo: State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resources and Hydropower Research, Beijing 100048, China
Jiandong Wang: Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China
Luhua Yang: College of Water Conservancy Engineering, Tianjin Agricultural University, Tianjin 300384, China
Shihong Gong: State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resources and Hydropower Research, Beijing 100048, China

Agriculture, 2022, vol. 12, issue 10, 1-17

Abstract: We created a subsurface drip irrigation (SDI)-specific variable flow emitter (VFE) that switches working stages automatically based on the inlet pressure ( H ) to achieve a step change in the flow rate. At working stage I ( H = 0.1 MPa), namely the conventional water supply stage, the VFE provided a normal flow rate ( q I ) of 1–2 L/h for crop irrigation. At working stage II ( H > 0.1 MPa; exceeding the design pressure), VFE delivered a larger flow rate ( q II ). The larger q II facilitated water movement upward from the underground to the surface seedbed during the crop planting, thus ameliorating crop germination issues under SDI. We focused on the impacts of four structural parameters of the flow channel: tooth height ( E ), tooth spacing ( B ), tooth angle ( A ), and flow channel depth ( D ) on the q I and VFE-flow index ( x ) at working stage I. Computational fluid dynamic (CFD) simulations were conducted along with a physical laboratory test to develop VFE using computerized numerical control (CNC) technology (accuracy = 0.05 mm). Nine VFEs were designed using an L9(3 4 ) orthogonal test. The combination of tetrahedral meshing with a six-layer boundary layer and the realizable k–ε turbulence model was found suitable for CFD simulations. The standard root-mean-square error (nRMSE) of the measured and simulated q Is was a minimum of 7.4%. The four parameters influenced q Is as D > B > E > A , and the four factors influenced the x s as B > E > D > A . Based on the numerical simulation data, multiple linear regression models were constructed for the q Is and x s with four parameters when H = 0.1 MPa. Aiming for the minimum x , the optimal combination of the flow channel structural parameters corresponding to different q Is was determined by the ergodic optimization algorithm. When q I was 1.5 L/h, the optimal structural combinations were E = 1.2 mm, B = 1.8 mm, A = 42°, and D = 1 mm. The VFE with a q I of 1.5 L/h was created by CNC technology. The relative errors of the measured and predicted q Is using the regression model were −0.19–6.31%, and their nRMSE was 6.76%. Thus, optimizing the flow channel structural parameters based on a multiple linear regression model and the ergodic optimization algorithm is a highly precise theoretical base for VFE development.

Keywords: subsurface drip irrigation; variable flow emitter; clogging; numerical simulation; flow index; iterative optimization algorithm (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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