Introducing a water dispersal needle has been shown to be an effective way of improving the uniformity of water distribution from irrigation sprinklers. However, the jet breakup mechanism remains unknown. Here, the impacts of key parameters, including the insertion jet depth (), cone angle (), and distance from the nozzle outlet (), on jet breakup phenomena were investigated by simulation. A comprehensive computational approach was used, which integrated the Volume-of-Fluid method with the model, overset grids, and adaptive mesh refinement technique. The results showed distinct jet field zones characterised by stable velocity, descent, rebound, and fluctuation zones, which were delineated by the axial average velocity profile. It was found that increasing , , or reducing results in a significant reduction of 7.73%, 5.04%, and 5.54% respectively in axial average velocity within the fluctuation zone. Augmentation of large-scale eddies, vortex bands, wave-like eddies, and vortex ring structures intensified the local entropy production rates, increased energy dissipation. The findings showed how this greatly influenced the throw radius of the sprinkler. Moreover, increasing , , or decreasing also increased air entrainment rates within the velocity decrement zone. This phenomenon was significant in the rebound and fluctuation zones, heightening the jet breakup and increasing the number of detached water droplets. Such dynamic interaction significantly influences the predicted water application rate within a 6-m radius of the sprinkler. Thus, this simulation study serves as a reference for comprehending the intricate jet breakup characteristics and the consequent sprinkler system hydraulic performance.

中文翻译：

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灌溉喷头中散水针射流破碎的数值模拟与实验研究

事实证明，引入水分散针是提高灌溉喷头水分配均匀性的有效方法。然而，射流破碎机制仍然未知。在这里，通过模拟研究了关键参数，包括插入射流深度（）、锥角（）和距喷嘴出口的距离（）对射流破碎现象的影响。使用了一种综合计算方法，将流体体积方法与模型、重叠网格和自适应网格细化技术相结合。结果显示出明显的射流场区域，其特征是稳定速度、下降、回弹和波动区域，这些区域由轴向平均速度剖面描绘。结果发现，增大 、 或减小，可使波动区内的轴向平均速度分别显着减小 7.73%、5.04% 和 5.54%。大规模涡流、涡带、波状涡流和涡环结构的增强加剧了局部熵产速率，增加了能量耗散。研究结果表明，这极大地影响了喷头的投射半径。此外，增加 、 或减少也会增加速度减小区内的空气夹带率。这种现象在反弹区和波动区很明显，加剧了射流破裂并增加了分离水滴的数量。这种动态相互作用显着影响喷头 6 米半径内的预测用水量。因此，该模拟研究可以为理解复杂的射流破碎特性和随之而来的喷水灭火系统水力性能提供参考。