Effect on spraying uniformity based on geometrical parameters and combined spacing of rotational fluidic sprinkler

Abstract: The rotational fluidic sprinkler was originally developed in China based on the theory of fluidic wall-attachment effect. To explore the relationships between geometrical parameters and spraying uniformity, the rotational fluidic sprinkler typed 10 was chosen as an object. Nine kinds of different offset length H, working area length L and contraction angle θ were specially fabricated. The parameter of H×L was 2.4 mm×20 mm, 2.6 mm ×24 mm or 2.8 mm×28 mm, and the θ was 10, 30, or 50 degrees. The laboratory conditions were set up in Jiangsu University of China. The catch-cans, which are 0.2 m in diameter and 0.6 m in height, were displayed in radial. The interval space was 1 m between any two of them and the number of used catch-cans was twelve in total. Experiments were carried out under the operating pressure of 300 kPa and the radial water distributions for the nine different nozzles were tested out. For the reason that every tested radial value represented different covered area, a mathematical model was established to transfer radial data into grid data. Therefore, the overlapped grid data in combined irrigation can be added directly to calculate out the combined uniformity coefficient. Rectangular layout and combined spacing with 8, 9, 10, 11, 12 and 13 m were chosen to analysis. A program was established using Matlab to draw three-dimensional water distribution and to calculate out the combined uniformity coefficient. The results showed that the average rotational time per circle was about 20 seconds. The water distribution was both affected by H×L and θ. With the increasing of H×L or θ, more irrigation intensity near the sprinkler and less irrigation intensity far from the sprinkler. Taking the nozzle where θ was 30 degrees, H×L was 2.6×24 mm and the combined spacing was 10 m as an example, the water distribution was relative equal all around the covered area, the combined irrigation intensity was between 1.5 to 6 mm per hour, and the highest irrigation intensity was 6 mm per hour in the middle of the four sprinklers. When H×L=2.4 mm×20 mm and H×L=2.6 mm×24 mm, the value and trend of combined uniformity coefficient were almost the same. The variable trend with combined spacing was more stable when H×L=2.8 mm×28 mm. The combined uniformity coefficient deviation was within 2% for different θ when combined spacing was 8 to 10m, and increased with θ when combined spacing was more than 10 m. For all of the nozzles in different combined spacing, the combined uniformity coefficient decreases as the increasing of combined spacing. The combined uniformity coefficient can be more than 75% and the average irrigation intensity was lower than 8 mm/h, which was satisfied with the sprinkler irrigation requirements. It is suggested that 10 to 12 m is the best combined spacing for the rotational fluidic sprinkle.