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Numerous methodologies have been developed to characterize sprinkler irrigation drops with the purpose of improving irrigation efficiency and controlling soil erosion and compaction. This paper presents the laboratory characterization of the morphology and velocity of drops in their free-falling trajectory as influenced by drop diameter and wind speed. For this purpose, a particle tracking velocimetry technique with in-line volumetric illumination was implemented. Hypodermic needles were used to produce droplets of uniform size. Two needle diameters resulted in drops with average diameters of 1.94 and 2.94 mm. Drops were illuminated with a double-pulsed laser beam or an LED lamp. Drop characterization reached an elevation of 4.28 m and occasionally attained terminal velocity. Motion blur was suppressed using a deconvolution filter. Drop equivalent diameter, velocity, chord ratio, canting angle and trajectory angle were determined using an ad-hoc software. The experimental approach led to the measurement of real drop size by illuminating a volume in the capture zone; drop shape ranged from quasi-sphere to ellipsoid. Drop deformation was more intense under high wind speeds. Ballistic simulations of drop fall were performed using sphere and ellipsoid drag force models. Both models resulted in excellent agreement with measured drop velocity, with the ellipsoid model performing marginally better. The robustness of the experimental equipment, particularly in combination with the developed LED lamp, announces future outdoor applications in real sprinkler irrigated fields. Such applications will provide insight on the governing processes, and data sets for the improvement of sprinkler simulation models. [ABSTRACT FROM AUTHOR]

Numerous studies have analyzed the solid-set sprinkler irrigation system performance. However, the effect of field-boundaries irrigation has not been considered in the whole-field performance. The objectives of this study were (1) to characterize two different solutions to irrigate field boundaries (full-circle sprinkler equipped with a deflecting plate, DP, and partial-circle sprinklers, PC); (2) to calibrate and validate a ballistic model to adequately simulate these solutions; and (3) to analyze the two different designs (DP or PC) from a whole-field perspective. Two types of experiments were designed. The first was carried out with an isolated sprinkler under no windy conditions to estimate drop size distribution parameters. The second was performed in a solid-set sprinkler layout under windy conditions to calibrate and validate the ballistic model. The experimental design allows the comparison of both solutions under equal technical and meteorological conditions. Comparisons between designs (DP or PC) were established for a whole-field area in terms of irrigation performance and crop yield. From a technical point of view, PC sprinklers perform better than DP sprinklers. From an economical point of view, the shape and orientation of the plot and the legal requirements of the irrigation system design (minimum distance of the sprinkler line to the border) have an important effect on the optimal solution to irrigate field boundaries. [ABSTRACT FROM AUTHOR]

A topographic three-dimensional scanner is similar to a radiometric total station, but it does not require a reflecting prism, and the optical measurement device is motorized and automated. With this device, very large survey data sets can be collected with moderate effort. In this paper, the application of a 3D scanner to surface and sprinkler irrigation research is presented and discussed. In surface irrigation, the scanner was successfully applied to (1) the survey of soil surface elevation, including furrowed areas; (2) the determination of flow cross-sections; (3) surveying the location of the advancing front and (4) measuring water surface elevation. The device showed some limitations in the measurement range, which was limited to about 35 m for water surface elevation and 50 m for the detail survey of furrowed areas. In sprinkler irrigation, the scanner was applied to the survey of the sprinkler jet and the irrigation drops during their trajectory. The scanner seemed to fail to survey fine drops, since falling drops were rarely scanned in the vicinity of the sprinkler. Despite the reported limitations, the 3D scanner seems to be destined to occupy a relevant place in the irrigation research laboratory. [ABSTRACT FROM AUTHOR]

The characterization of drops resulting from impact sprinkler irrigation has been addressed by a number of techniques. In this article, a new technique based on low-speed photography (1/100 s) is presented and validated. The technique permits to directly measure drop diameter, velocity and angle. The photographic technique was applied to the characterization of drops resulting from an isolated sprinkler equipped with a 4.8 mm nozzle and operating at a pressure of 200 kPa. Sprinkler performance was characterized from photographs of 1,464 drops taken at distances ranging from 1.5 to 12.5 m. It was possible to analyze separately the drops emitted by the main jet and those emitted by the impact arm. The proposed technique does not require specific equipment, although it is labor intensive. [ABSTRACT FROM AUTHOR]

A numerical study of the magnetic induction equation has been performed on von Kármán type flows. These flows are generated by two co-axial counter-rotating propellers in cylindrical containers. Such devices are currently used in the von Kármán sodium (VKS) experiment designed to study dynamo action in an unconstrained flow. The mean velocity fields have been measured for different configurations and are introduced in a periodic cylindrical kinematic dynamo code. Depending on the driving configuration, on the poloidal to toroidal flow ratio and on the conductivity of boundaries, some flows are observed to sustain growing magnetic fields for magnetic Reynolds numbers accessible to a sodium experiment. The response of the flow to an external magnetic field has also been studied: The results are in excellent agreement with experimental results in the single propeller case but can differ in the two propellers case. [ABSTRACT FROM AUTHOR]