Comprehensively evaluating and modelling droplet diameters and kinetic energies of low‐pressure sprinklers

Abstract

Proper droplet diameter and kinetic energy can effectively reduce the risk of soil erosion during low-pressure sprinkler irrigation. In this study, we comprehensively evaluated the radial distributions of droplet diameter, velocity, kinetic energy, kinetic energy per unit droplet volume, and specific power for three common low-pressure sprinklers, i.e. Nelson D3000, R3000 and Komet KPT, with two operating pressures (103 and 138 kPa) and three nozzle outlet diameters (3.97, 5.95 and 7.94 mm). Additionally, the relationships between these droplet characteristic parameters were analysed. Overall, the maximum values of five characteristic parameters were observed at the end of the jet under various treatments. Although R3000 had a larger droplet diameter (0.10-6.42 mm) and kinetic energy (1.08 Â 10 À10 -8.59 Â 10 À3 J) distribution range than D3000 and KPT, the D3000 specific power (mean value of 0.4274 W m À2 ) was the highest of the three sprinklers. Therefore, KPT was suggested more in low-pressure sprinkler irrigation than in the other two sprinklers because its application rates were reduced along the radial direction. In addition to selecting a suitable sprinkler type for minimizing specific power, determining a reasonable sprinkler spacing was also significant (P < 0.01). Furthermore, a universal specific power model with an appropriate accuracy (RMSE = 0.011 W m À2 , NRMSE = 29%) was proposed. This study provides a key basis for the selection and combination of low-pressure sprinklers.droplet diameter, kinetic energy, low-pressure sprinklers, specific power, universal model Résumé Un diamètre de gouttelettes et une énergie cinétique appropriés peuvent réduire efficacement le risque dérosion des sols lors de l'irrigation par aspersion à basse pression. Dans cette étude, nous avons évalué de façon complète les distributions radiales du diamètre des gouttelettes, de la vitesse, de l'énergie cinétique, de l'énergie cinétique par unité de volume des gouttelettes, et de la puissance spécifique pour trois sprinklers courants à basse pression, à savoir Nelson D3000, R3000 et Komet KPT, avec deux pressions de fonctionnement (103 et 138 kPa) et trois diamètres de sortie de la buse (3,97, 5.95 et 7.94 mm). De plus, Article title in French: Evaluation et modélisation complètes des diamètres de gouttelettes et des énergies cinétiques des sprinklers basse pression.

Sprinkler Irrigation on Sloping Land: Distribution Characteristics of Droplet Impact Angle and Shear Stress

“…Similar outcomes in sprinkler irrigation experiments on flat land have been observed by other researchers [18,21,33]. This was expected because small diameter droplets predominate near the sprinkler [16,34,35]. Meanwhile, the specific surface area (surface area per unit volume) of the small droplet is large [36]; therefore, its air friction resistance ratio is relatively high, and the horizontal droplet velocity rapidly approaches zero [37].…”

“…However, the sprinkler droplets that continue to hit the soil can easily cause soil surface sealing, resulting in surface runoff on sloping land and affecting the absorption of water by crops [9,10]. Results from previous studies have suggested that soil surface sealing is mainly due to the separation of soil particles from aggregates [11,12], and it is generally considered to be closely related to sprinkler droplet kinetic energy [13][14][15][16].…”

“…Therefore, Hui et al [21] used a two-dimensional video disdrometer (2DVD) to investigate the droplet impact angle distributions of a ball-driven sprinkler and established the relationships between droplet impact angles and shear stresses. Moreover, Hui et al [16] also selected the three low-pressure sprinkler types, i.e., Nelson D3000, R3000, and Komet KPT, for research and observed that with the increase of distance from the sprinkler, the droplet impact angle decreased and velocity increased, which resulted in a significant enlargement in the shear stress. These aforementioned research results provide another scientific method for accurately predicting soil erosion and designing irrigation engineering under sprinkler irrigation.…”

Non-negligible factors in low-pressure sprinkler irrigation: droplet impact angle and shear stress

“…As one of the common high-efficiency water-saving irrigation devices in farmland, the center pivot irrigation system has rapidly applied in China in recent years due to its advantages including high irrigation efficiency, wide coverage of irrigated area, high automation, and low labor costs (Yan et al, 2020;Baiamonte et al, 2021;Hui et al, 2022a). By the end of 2019, there were more than 18×10 3 sets of center pivot and linear-move irrigation systems used in China, with an irrigation area of nearly 6×10 5 hm 2 , which accounted for about 14.2% of the total sprinkler irrigation area (Hui et al, 2022b). With the global objective of peaking the carbon emissions and carbon neutrality, it is imperative to realize the low-pressure and energy-saving sprinkler irrigation.…”

“…Nonetheless, the strong wind resistance characteristics of OSPS make it highly competitive in the sprinkler marketplace (Manke et al, 2019). Nowadays, numerous studies have focused on the water application rate, droplet diameter, kinetic energy, and other indicators of low-pressure sprinklers (Yan et al, 2010;Sayyadi et al, 2014;Robles et al, 2019;Hui et al, 2022b). However, the impact angle and shear stress of the droplet have rarely been investigated, which is not conducive to further revealing the soil erosion mechanism under low-pressure sprinkler irrigation.…”