View of the reconnection of the vortex line and its acoustic emission

通过光学实验研究了可压缩涡环在头部碰撞和斜碰撞以及涡环靠近平面壁时的流场和涡流结构。在环流和后续流动诱导的壁面边界层上产生一个强分离气泡，并发展出二次涡。在所有情况下都可以看到，在相互靠近的两个涡核之间形成了一个向内的新激波。这一激波的形成机理与收敛-扩张喷管流动相同。这意味着强涡核的作用方式与喷嘴相似。当两个涡环接近时，涡芯线上发展出小幅度、短波长的不稳定性。波浪型涡芯线在接触点开始卷曲。迎头相撞的涡线在高速时沿径向拉伸，并在涡核线周围扩展为湍流云。在斜碰撞中，接触点处的涡环围绕涡线展开盘绕。反平行的涡流被抵消，涡线显示出重联的结构。涡线重联过程中的形态结构类似于计算的涡系结构。分离气泡形成的二次涡环从壁面上升，从外部进入一次涡旋的内部。当涡核相互缠绕时，在所有情况下都会产生声波。

Optical experimental studies have been performed to understand flowfield and vortex structures in the head on collision and the oblique collision of two compressible vortex rings, and in the vortex ring approaching a plane wall.When the vortex ring comes close to the rigid wall, a strong separation bubble is generated from the wall boundary layr induced by the ring and the following flow and develops the secondary vortex.It is seen in all cases that an inward facing new shock is formed between the cores of two vortices approaching each other.The formation of this shock is the same mechanism in the convergent-divergent nozzle flow.It means that the strong vortex cores act in a way similar to the nozzle.As the two vortex rings approach, the instability with the small-amplitued and short-wavelength develops on the vortex core lines.The wavy vortex core lines begin to wind round at the point of contact.The vortex lines coming into a head-on collision are stretched in the radial direction at the high speed, and expand to a turbulent cloud around the vortex core lines.In the oblique collision, the vortices at the contact points stretches and coil around the vortex line.The anti-parallel vortices are canceled and the vortex lines show the structure of the reconnection.Morphological structures on the process of reconnection of the vortex lines resemble to computed vortex structures.The secondary vortex ring developing from the separation bubble rise from the wall, and get in the interior of the primary vortex from the outside.The sound waves generate in all cases when the vortex cores wind round each other.