横向气流中非牛顿液体射流直接数值模拟

采用直接数值模拟研究了动量比为6的非牛顿液体射流在横向气流中的破碎特征，重点分析了表面波发展、弯曲特性和展向扩散等射流结构及其非牛顿特征。在非牛顿液体射流的近喷嘴位置，其表面迹线随时间摆动，并有逆横向气流方向运动的趋势。射流的展向扩散仅在喷入初期较为明显，此后基本维持在接近35°的扩散半角。射流的一次破碎，尤其是液丝与液滴、甚而卫星液滴的生成过程都被精细地捕捉和描述。在近喷嘴的射流柱附近，横向气流流动具有一定的圆柱扰流相似性，在其他区域则表现为极其复杂的紊流特征。射流的非牛顿特性主要体现在黏性系数，不同位置的液体黏性系数相差超过20%。相较牛顿液体射流，剪切稀化的非牛顿射流具有更易破碎的特征。

Direct numerical simulation of a non-Newtonian liquid jet in crossflow

A direct numerical simulation study of a non-Newtonian liquid jet in crossflow is carried out with a moderate momentum flux ratio 6. The emphasis of this paper mainly focuses on the flow structure of the jet, including surface behaviors, bending phenomena, spreading features and non-Newtonian characteristics. Deep into the near-field region, it can be observed that the trajectory of the jet oscillates with time and has a tendency to move backward in the reverse direction of the crossflow. The spreading angle increases only at the start of the injection but keeps nearly constant afterwards at 35°. Further insight into the flow physics is obtained by visualizing the primary breakup of the jet, especially the formation of ligaments and droplets, as well as satellite droplets. In the near-field region, the flow feature is similar to that of a circular cylinder, while showing complex turbulent behavior in other regions. The specific non-Newtonian characteristics of the fluid are observed by analyzing the shear thinning viscosity, which varies over 20% spatially inside the liquid. Compared to Newtonian fluids, the current shear thinning non-Newtonian liquid jet shows a stronger breakup feature.