Abstract

In this study, two vortex rings composed of upper fluid were continuously ejected vertically downward toward the interface of the two-layer density-stratified fluid. The motion of the vortex rings and behavior of the lower layer fluid were investigated via visualization experiment, and the effect of time interval between the injections of the two vortex rings on the mixing of the density-stratified fluid was investigated. The first emitted vortex ring (VR_A) advected vertically downward in the upper layer, passed through the density interface, and then advected in the lower layer. After VR_A reached the maximum depth in the lower layer, the upper part of the fluid mass ejected into the upper layer due to buoyancy. The lower fluid was entrained in the upper layer. Subsequently, a new vortex ring (VR_C) was generated by the fluid mass ejected in the upper layer and advected vertically upward in the upper layer. The second vortex ring emitted (VR_B) collided with the tip of the fluid mass of the VR_A ejected from the lower layer. Subsequently, it slightly penetrated the lower layer, rolled up the lower layer fluid into the upper layer, and coalesced with VR_C to collapse. In the process of vortex merging, the mixing of the upper and lower layers reached a maximum when the VR_A reached the maximum depth. Furthermore, it was clarified that the mixing ability of the upper and lower layers depends on the ejection time interval of the two vortex rings.

Graphic abstract

中文翻译：

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通过两个涡流环将两层密度分层的流体依次向密度界面发射

摘要

在这项研究中，由上部流体组成的两个涡流环连续垂直向下朝两层密度分层流体的界面喷射。通过可视化实验研究了涡流环的运动和下层流体的行为，研究了两个涡流环之间的喷射时间间隔对密度分层流体混合的影响。第一个发射的涡流环（VR _A）在上层垂直向下平移，穿过密度界面，然后在下层中平移。之后VR_一到达下层的最大深度时，由于浮力，上部的流体物质喷入上层。下部流体夹带在上层中。随后，通过在上层喷射并在上层垂直向上平移的流体物质产生了新的涡流环（VR _C）。发射的第二涡流环（VR _B）与从下层喷射的VR _A的流体质量的尖端碰撞。随后，它略微渗入下层，将下层流体卷入上层，并与VR _C合并以塌陷。在涡旋合并过程中，当涡旋合并时，上层和下层的混合达到最大。VR _A达到最大深度。此外，澄清了上层和下层的混合能力取决于两个涡流环的喷射时间间隔。

图形摘要