Abstract:Abstract: Spray jets in the overlap region of adjacent sprinklers come from different applicators. Collisions and other interactions in the injection process are inevitable. However, the water distribution of a single sprinkler nozzle is always used to calculate the combination of sprinkler irrigation uniformity by giving an overlapping space due to the limitations of test site, sprinklers layout or other conditions. To study the effect of jets interaction on the overlapped spray characteristics between adjacent sprinklers, two different types of sprinklers were selected, namely, Nelson D3000 sprinkler with coarse jagged plate and Nelson R3000 rotating spray plate sprinkler. Water distribution pattern and droplets spectrum were measured and compared with the two nozzles spraying separately and simultaneously, with a combinatorial space of 2.5 m. The water distribution and raindrop spectrum of separately sprinkling were added together as theoretical combination (TC) while the simultaneously sprinkling was named actual superposition (AS). The results showed that the strength of interaction between sprinklers was influenced by geometry structure of nozzle. The influence of jets interaction on Nelson R3000 rotating spray plate sprinkler was not significant. In contrast, Nelson D3000 sprinkler with coarse jagged plate was severely affected by the effect of jets interaction, and the water application rate and kinetic energy had obvious redistribution along the radial direction. The location of precipitation concentrated points had an offset due to the change of jets trajectories and the point with maximum precipitation intensity moved 0.5 m closer to the sprinkler nozzle. At the measuring point of 2.5 m, the application rate, energy flux density and droplet number of AS increased by 91.27%, 107.58% and 239.29% when compared with TC. The increase of the number of droplet size grater than 0.9 mm showed great contribution to the water and energy rise at this measuring point, and the contribution rate reached 40.89% and 58.83%, respectively. Both the drop landing velocity and landing angle under AS condition were lower than that under TC condition. Under TC condition, the largest drop landing velocity and landing angle were 6.01 m/s and 75.38o while the values changed into 4.59 m/s and 63.91o under the condition of AS. The droplets spectrum variability analysis of the overlapping region reflected that the redistribution of water application rate and kinetic energy was mainly due to the increasing probability of droplets collision when multi-sprinklers were spaced for irrigation. Water droplets changed original trajectories by the effect of external forces, and interacted with other droplets to form bigger size of drop or dispersed into a large number of tiny droplets. The strength of jets interaction should be considered when calculating the overlapped water application rate with a relatively small space, a direct superposition of single sprinkler water distribution might cause distortion of the results. This study on spraying hydraulic performance tests were carried out in fixed nozzle under indoor conditions, and further studies on multiple nozzles under mobile condition are needed to determine the impact of jet interaction on the spray characteristics.