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研究生:沈志鴻
研究生(外文):Chih-Hung Shen
論文名稱:漩渦內流場多重流場結構之數值探討
論文名稱(外文):Numerical Investigations on Multiple Structures of Confined Swirling Flows
指導教授:江滄柳
指導教授(外文):Tsang-Leo Jiang
學位類別:碩士
校院名稱:國立成功大學
系所名稱:航空太空工程學系
學門:工程學門
學類:機械工程學類
論文種類:學術論文
論文出版年:1993
畢業學年度:81
語文別:中文
論文頁數:68
中文關鍵詞:漩渦內流場多重流場結構紊流模式數值擴散
外文關鍵詞:Confined Swirling FlowsMultiple Flow StructuresTurbulence
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關於漩渦紊流場,由於其廣泛應用於各種燃燒室的設計上,可藉由適當的
設計來達到增加油氧混合效率、縮短火燄長度及降低污染產物等目的,亦
可利用其提供良好的穩定火燄效果而取代助燄器之設計,因此近年來受到
相當的研究與重視。但由於其流場中因漩流與紊流互相耦合所導致的複雜
現象,因此對數值模擬而言仍是一個具挑戰性的課題。一般認為對此類流
場無法準確模擬的主要原因為:紊流模式的限制,缺乏完整而正確的入口
條件,以及數值擴散效應的影響。最近本研究小組對漩渦內流場的研究中
更發現了在某流場條件下存有多重流場結構的現象,本文乃對此問題做進
一步之研究探討。研究的結果指出:當流場中內迴流區及外迴流區的大小
相當時,將發生多重流場結構現象。而內外迴流區的大小,不僅受流場條
件的影響,所用的數值方法、格點及物理模式均有影響。因此前人關於
k-.epsilon. 紊流模式不適於此類流場的結論有重新評斷之必要,因為某
些與實驗數據差距較大的數值結果可能因其所得的數值模擬結果恰為多重
流場結構中較偏離實驗的那組結果。

Turbulent swirling flow has drawn considerable attention in the
past decades since it possesses wide-range applications in many
practical combustion devices. It promotes mixing of fuel and
air, reducing flame lengths and pollutant emission. It also
provides good flame stabilization such that the flame holding
mechanisms installed in the combustor can be eliminated.
However, due to its complexity associated with the coupling of
turbulence and swirling, it is still a challenging subject for
numerical studies. Turbulent swirling flow calculations can be
inaccurate due to at least three major reasons: limitations of
the turbulence modeling used, incorrect or inadequate
specifications of inlet boundary conditions, and error
introduced through the numerical diffusion. Furthermore,
multiple flow structures for confined swirling flows were
found at certain flow conditions by our group recently. This
finding has significant impacts on the swirling flow study and
is further investigated in this thesis. The numerical results
obtained in the present study reveal that, when the sizes of
internal and external recirculation zones are exhibited to be
comparable, multiple flow structures result. The internal and
external recirculation zone sizes, however, depend upon not
only the flow conditions but also the employed numerical
scheme, grid system, and physical models. It is found that the
previous arguments regarding k-.epsilon. model's performance
should be reexamined since some previous computational results,
which deviated significantly from the experimental results,
just fell into the other branch than the one for the
experimental conditions.

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