本研究之目的為分析噴流液柱在不同流率和旋轉速度條件下的特徵變
化。研究中以常溫的水為工作流體，將液柱噴嘴搭配一組可調速的旋轉機構，藉由改變不同的液柱直徑(dj)、流體流率(Q)與噴嘴旋轉速率(w)，以探討液柱長度( j L )與液柱斷裂成液滴之特性。此實驗證實外部旋轉將會使得液柱的斷裂長度減少，且隨著轉速上升其斷裂長度更加縮短，此外，在同一轉速、流量的情況下，較大的液柱直徑受旋轉效應明顯，其縮短幅度加劇。在較大液柱直徑(>1100 micrometer)之實驗中，噴流液柱會有遲滯現象(Hysteresis)的發生，即是在間歇滴落區(D)時，將其流量增加而達到液柱型態(J)，與流體處在液柱型態區(J)將其流量減低而達到間歇滴落區(D)時所面臨的臨界流量並不相同。而在液滴成型方面，依實驗結果將液柱斷裂型態分為: 穩定液滴、兩顆液滴追撞與多顆液滴追撞。研究結果發現，旋轉效應會使得液柱斷裂更加不穩定，兩顆液滴追撞或是多處頸縮(Multi-position Necking)造成之多顆液滴追撞將會頻繁產生。

This research is dedicated to analyzing the characteristic of a liquid jet under various conditions, for example, under different flow rates and rotating speeds. In this study, we found that the imposed rotation would shorten the breakup length of a liquid jet due to the extra disturbance. On the other hand, hysteresis behavior occurred during the use of relatively large nozzle diameters, which indicates that the critical flow rate of the transition from dripping to jetting (DJ) is different from that from jetting to dripping (JD). Consequently, we further analyzed the critical rotating speed (JD) and the critical flow rate (DJ) in this hysteresis zone. As for the last part of this study, once the breakup patterns had been deduced, we could divide the breakup modes into three distinguishable patterns basically by how the droplets formed: steady formation, two-drop coalescence, and multiple-drop coalescence, respectively. Lastly, the mutual interaction between these three patterns and how the rotation affected the outcomes of the liquid jet were determined in this research.

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