Japan Aerospace Exploration Agency Institute of Aerospace Technology
Japan Aerospace Exploration Agency Institute of Aerospace Technology
Japan Aerospace Exploration Agency Institute of Aerospace Technology
Japan Aerospace Exploration Agency Institute of Aerospace Technology
Nagoya University Graduate School of Engineering
JAXA Special Publication: Proceedings of 39th Fluid Dynamics Conference/Aerospace Numerical Simulation Symposium 2007
巻
JAXA-SP-07-016
ページ
160 - 165
発行年
2008-02-29
抄録（英）
This paper presents a numerical study on ligament breakup mechanism due to capillary force. In contrast to the classical Rayleigh analysis, the effect of ligament tip is included to examine the role of capillary waves from the tip. The numerical setup corresponds to a series of microgravity experiments conducted at Nagoya University. Based on Weber's similarity law (We is approximately O(1)), a low-speed jet of liquid SF6 is injected into high-pressure (9.1 MPa) ambient nitrogen and short-wave breakup that is different from Rayleigh's analysis is observed in the experiment. The present numerical simulation has reproduced the same pinch-off and shown that droplet pinch-off from the tip is a combination of multiple phenomena. One is the short-wave breakup. Capillary waves from the tip propagate upstream, become unstable and lead to droplet formation at the tip. This is a closed and self-sustained cycle. This destabilization process is driven by the dynamics of the tip bulb and capillary waves. The elongation by the gas flow also strengthens the pinch-off. As the liquid column length becomes longer, the other mode of long-wave instability also appears. This mode corresponds to the convective Rayleigh mode. Short capillary waves from the tip reach the nozzle exit and are reflected. They become the source of this convective instability. The present study has shown that the ligament tip plays an important role in droplet breakup.
表面張力による液糸分断機構の解明に関する数値解析
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