DIMSUB, a computer program for designing microirrigation subunits: tool definition and case studies

DIMSUB is a computer program to complement a decision support tool (DST) to effectively study different hydraulic design alternatives in microirrigation systems. We developed environments in Visual Basic for applications for Microsoft Excel® that allow specific step-by-step functions to be created for the design of irrigation subunits. Different alternatives can be considered, such as types of emitter, lateral and submain pipe sizes, different feeding points, irregular subunit shapes and topography slopes. Furthermore, specific uniformity criteria need to be considered to achieve efficient water applications and proper design systems. Lengths of run lateral and submain pipes, position of the hydrant connection, pressure head and head loss in pipes or pressure-compensating emitters can be assigned to evaluate the results and choose the best design alternative. This user-friendly tool to study hydraulic variables is expected to be a valuable aid for the decision-making process in designing irrigation systems. Some examples of practical cases under specific crop conditions to design drip irrigation subunits are given using DIMSUB.

DIMSUB, a computer program for designing microirrigation subunits: tool definition and case studies

DIMSUB is a computer program to complement a decision support tool (DST) to effectively study different hydraulic design alternatives in microirrigation systems. We developed environments in Visual Basic for applications for Microsoft Excel® that allow specific step-by-step functions to be created for the design of irrigation subunits. Different alternatives can be considered, such as types of emitter, lateral and submain pipe sizes, different feeding points, irregular subunit shapes and topography slopes. Furthermore, specific uniformity criteria need to be considered to achieve efficient water applications and proper design systems. Lengths of run lateral and submain pipes, position of the hydrant connection, pressure head and head loss in pipes or pressure-compensating emitters can be assigned to evaluate the results and choose the best design alternative. This user-friendly tool to study hydraulic variables is expected to be a valuable aid for the decision-making process in designing irrigation systems. Some examples of practical cases under specific crop conditions to design drip irrigation subunits are given using DIMSUB.(AU)

Numerical study of upstream disturbances on the performance of electromagnetic and ultrasonic flowmeters

Electromagnetic and ultrasonic flowmeters are high precision devices that can measure the water flow in pressurized irrigation networks. In these networks, the inadequate installation distance of flow control valves generates upstream disturbances which will increase measurement errors and reduce the accuracy of the equipment. Therefore, estimating these errors is important to establishing the correct installation distance of the hydraulic accessories and to ensuring the metrological reliability of the flowmeters. This work proposes a numerical study using Computational Fluid Dynamics to evaluate water flow behavior in pipes and estimate measurement errors caused by gate and butterfly valves in installation configurations found at pressurized irrigation networks. The numerical simulations were made for gate (15, 50 and 75 % closed) and butterfly (open and 30º closed) valves installed three and six diameters (3D and 6D) from the flowmeters. The numerical study with three-dimensional simulation allows for evaluating the flow behavior and estimating measurement errors correctly. According to the study, the installation configurations of the gate and butterfly valves change the flow velocity profile at different positions in the pipe, generating both positive and negative measurement errors at both flowmeters. Among the tested configurations, only the butterfly valve installed 3D and 6D from the electromagnetic flowmeter ensured the measurement accuracy required by ISO 4064.

Numerical study of upstream disturbances on the performance of electromagnetic and ultrasonic flowmeters

Electromagnetic and ultrasonic flowmeters are high precision devices that can measure the water flow in pressurized irrigation networks. In these networks, the inadequate installation distance of flow control valves generates upstream disturbances which will increase measurement errors and reduce the accuracy of the equipment. Therefore, estimating these errors is important to establishing the correct installation distance of the hydraulic accessories and to ensuring the metrological reliability of the flowmeters. This work proposes a numerical study using Computational Fluid Dynamics to evaluate water flow behavior in pipes and estimate measurement errors caused by gate and butterfly valves in installation configurations found at pressurized irrigation networks. The numerical simulations were made for gate (15, 50 and 75 % closed) and butterfly (open and 30º closed) valves installed three and six diameters (3D and 6D) from the flowmeters. The numerical study with three-dimensional simulation allows for evaluating the flow behavior and estimating measurement errors correctly. According to the study, the installation configurations of the gate and butterfly valves change the flow velocity profile at different positions in the pipe, generating both positive and negative measurement errors at both flowmeters. Among the tested configurations, only the butterfly valve installed 3D and 6D from the electromagnetic flowmeter ensured the measurement accuracy required by ISO 4064.(AU)