海洋气-液两相输流复合材料立管双向耦合涡激振动特性分析

为了研究深海油气开发中输送气-液两相复合材料海洋立管的涡激振动,本文对新型复合材料立管在气-液两相内流及海洋外流共同作用下,其横流向和顺流向耦合涡激振动特性进行了分析和研究。基于Hamilton变分原理建立了考虑气-液两相流输运特性、内流流速、轴向顶张力及纤维复合材料特性影响的立管横流向和顺流向耦合振动控制方程,采用尾流振子模型模拟海流对细长复合材料立管的涡激力。利用Newmark-β和四阶Runge-Kutta耦合迭代法求解耦合动力学方程,定量地分析了内流液相流速、气体体积分数以及纤维铺层角对复合材料海洋立管横流向和顺流向涡激振动特性的影响。数值结果表明,立管的振动形态与液相流速呈正相关,与气体体积分数和纤维铺层角呈负相关,并且液相流速、气体体积分数和纤维铺层角对顺流向的偏移量比横流向的影响更大;在振动位移最小的位置处,复合材料立管的运动多为准周期或者混沌形式;立管横流向的弯曲应力对于参数的改变相对于顺流向更加敏感,存在“跳跃”改变现象。

DNS analysis of incipient drop impact dynamics using an accurate level set method

A series of 2D direct numerical simulations were performed with an accurate level set method for single drop impacts.The adopted ACLS method was validated to be efficient with perfect mass conservation in both normal and oblique impacts.A square-root correction for neck bases was modified in accuracy as well as scope of applications.In addition,process of jet formation and evolution was studied to reveal internal dynamics in drop impacts.It's found that pressure gradient and vortex are coexisting and completive reasons for jet topology while the inclined angle has a significant effect on them.Mechanisms of jet formation and evolution are different in the front and back necks.With the help of PDF distribution and correction calculation,a compromise in the competition is observed.This work lays a solid foundation for further studies of dynamics in gas-liquid flows.