Fukuoka Institute of Technology, Wajiro-higashi, Higashi-ku, Fukuoka 811-0295, Japan.
Kyushu University, Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
Phys Rev E. 2016 Jun;93(6):062214. doi: 10.1103/PhysRevE.93.062214. Epub 2016 Jun 14.
When a droplet with a higher density falls in a miscible solution, the droplet deforms and breaks up. The instability of a vortex ring, formed by droplet deformation during the falling process, causes the breakup. To determine the origin of the instability, the wavelengths and thicknesses of the vortex rings are investigated at the time when the instability occurs. The experimental results are almost in agreement with the calculated results for the Rayleigh-Taylor instability using the thickness of a higher-density solution. Furthermore, we performed simulations considering the torus shapes and circulations of the vortex ring. The simulations provided patterns similar to those observed experimentally for the breakup process, and showed that the circulations suppress the instability of the vortex ring. These results imply that the Rayleigh-Taylor instability plays a dominant role in the instability of vortex rings.
当密度较高的液滴在可混溶液中下落时，液滴会发生变形和破裂。液滴在下落过程中变形形成的涡环不稳定性导致了破裂。为了确定不稳定性的起源，研究了在不稳定性发生时涡环的波长和厚度。实验结果与使用高密度溶液厚度的瑞利-泰勒不稳定性的计算结果几乎一致。此外，我们还进行了考虑涡环形状和环流的模拟。模拟结果提供了与实验观察到的破裂过程相似的模式，并表明环流抑制了涡环的不稳定性。这些结果表明，瑞利-泰勒不稳定性在涡环不稳定性中起主导作用。
