平面激波冲击并排液滴的三维数值模拟研究

采用三维守恒清晰界面数值方法, 研究平面激波冲击并排液滴的动力学过程. 研究的焦点在于激波接触液滴后的复杂波系结构生成, 以及并排液滴相互耦合作用诱导的单个液滴非对称界面演化. 首先, 分析并排液滴之间界面通道内的波系结构发展, 发现在冲击初期由于反射激波相交而形成新的反射激波以及马赫杆; 这些流动现象与液滴另外一侧 (非通道侧) 由激波反射所形成的弯曲波阵面截然不同, 而且所导致的液滴横向两侧流场差异是中后期冲击过程液滴两侧界面非对称演化的主要原因. 其次, 研究冲击中期时, 特别是入射激波已运动至液滴下游并远离并排液滴, 界面形态的演化过程和规律, 揭示通道下游出口处由于气流膨胀导致的界面闭合、以及随后气流阻塞导致的界面破碎等新的流动现象. 最后, 研究液滴间距对并排液滴相互作用的影响规律, 发现液滴间距大小与通道内压力峰值具有明显的关联关系. 研究表明, 更小的液滴间距不仅带来更大的压力峰值, 而且使得峰值出现的时间更早. 

IMPACT OF A PLANAR SHOCK ONTO SIDE-BY-SIDE DROPLETS: A 3D NUMERICAL STUDY

In this paper we investigate the evolution dynamics of side-by-side droplets after being impacted by a planar shock by using a three-dimensional conservative sharp interface method. Our research mainly focuses on the development of wave structures after the shock impact and the asymmetric interface evolution of single droplet induced by the coupling between the side-by-side droplets. Firstly, we analyze the development of the wave system including those inside and outside the channel between the side-by-side droplets. We find that at the early stage of impact, the intersection of reflected shock waves accounts for the formation of new reflected shock waves and Mach rods. This is quite different from the curved wave front formed by the reflected shock wave on the other side of the droplet transversely opposite to the channel. The difference of the flow field on the two sides of the droplet is responsible for the asymmetric interface evolution of the droplet in the middle stage of the droplet-shock interaction. Secondly, we investigate the interface morphology and its evolution in the middle stage of shock impact, especially when the incident shock wave moves to the downstream of and is far away from the droplets, and report the occurrence of new flow phenomena at the downstream outlet of the channel, such as interface coalescence caused by airflow expansion and subsequent interface fragmentation owing to airflow blockage. Finally, the effect of the gap between the side-by-side droplets on the droplet interaction is studied. We find that the gap size has a significant effect on the occurrence of pressure peaks in the channel. Specifically, a smaller gap not only brings higher pressure peak, but also makes the peak appear at an earlier time.