臺灣博碩士論文加值系統

本研究主旨在於觀察單一圓柱與雙圓柱在剪切流場內的運動模式，探討圓柱於剪切流內是否具有流體-彈性不穩定現象(Fluid-Elastic Instibility)，並另外針對不同圓柱間距比、剪切參數以及質量比等參數，對於圓柱運動軌跡與振幅之影響，做詳細的分析。研究中運用計算流體力學軟體Fluent 6.3.26版本，求解此類問題；以SIMPLEC演算法將連續與動量守恆方程式做交替運算，並與圓柱運動方程式相結合，利用動網格技術，使圓柱體受到流場作用力的影響而產生運動；於不同流場條件下，模擬流場型態和圓柱運動模式，觀察鎖定(Lock-In)現象以及流體-彈性振動對圓柱體的影響。研究結果顯示，均勻流場中單一圓柱體的流場型態和運動模式與相關文獻互相吻合，而在剪切流場中，隨著剪切參數的增加，圓柱出現流體-彈性振動的情形，使圓柱振幅大幅提升。另外，在剪切流場中雙圓柱體的探討方面，以並列(Side-by-Side)與縱列(Tandem)的圓柱體排列方式下，調整圓柱間相對距離，均觀察出有流體-彈性振動現象的產生，與單一圓柱體相比較，其發生流體-彈性振動之臨界流速均小於單一圓柱體，代表著雙圓柱體流場較易發生流體-彈性不穩定現象。

This research is aimed to investigate the fluid-elastic instability of the motion simulation using a single cylinder and two cylinders within the context of shear flows. T/D, shear parameter and mass ratio are parameters to be investigated. Besides, cylindrical motion treks and the amplitude are also analyzed.
Continuity equation and momentum equations are solved alternatively using a CFD package, Fluent 6.3.26. The force caused by the flow interacts with the cylindrical motion. Thus Motion meshing techniques together with the cylindrical motion equations are employed in the simulation. Under different flow conditions, flow types and cylindrical motion models, lock-in and fluid-elastic instability are studied.
The results show that motion and flow types of a single cylinder within the context of the uniform flow have a general agreement with the related literatures. In terms of the shear flow, however, as the shear parameter increases, the fluid-elastic instability is caused, and thus amplitude of the cylinder augments considerably. Further, double cylinders in the shear flow are studied. Double cylinder arrangements( classified as side-by-side and tandem) and the distance between cylinders are the factors to cause fluid-elastic instability. Compared with the single cylindrical motion, double cylindrical motion’s critical flow velocity is smaller than the single cylindrical motion, which means double cylindrical motion are more subject to fluid-elastic instability.

第一章 緒論-----------------------------------------------------------------------1
1.1 研究動機------------------------------------------------------------1
1.2 文獻回顧------------------------------------------------------------3
1.3 研究目的------------------------------------------------------------8
1.4 研究中所使用的無因次參數定義-----------------------------9

第二章 模擬理論與數值參數設定------------------------------------------11
2.1 理論分析----------------------------------------------------------11
2.1.1 數值方法---------------------------------------------------12
2.1.2 流體統御方程式------------------------------------------12
2.1.3 圓柱運動方程式------------------------------------------13
2.1.4 數值運算流程---------------------------------------------15
2.1.5 SIMPLEC演算法-----------------------------------------18
2.2 數值參數設定----------------------------------------------------19
2.2.1流場的基本假設與邊界條件設定---------------------19
2.2.2流場計算域(Domain)的設定與測試------------------20
2.2.3流場系統的網格設定與測試---------------------------21
2.2.4時間步階的設定與測試---------------------------------23

第三章 結果與討論------------------------------------------------------------24
3.1 單一圓柱之理論驗證-------------------------------------------24
3.1.1 升力係數與阻力係數變化------------------------------24
3.1.2 史卓荷數變化---------------------------------------------25
3.1.3 流場型態變化---------------------------------------------26
3.2均勻流場中單一彈性圓柱之運動模式探討-----------------27
3.2.1 無因次速度與圓柱振幅變化---------------------------27
3.2.2 無因次速度與頻率比變化------------------------------28
3.2.3 質量比對圓柱振幅之影響------------------------------29
3.2.4 圓柱運動軌跡變化---------------------------------------30


3.3剪切流場中單一彈性圓柱之運動模式探討-----------------31
3.3.1 剪切參數對圓柱振幅之影響---------------------------32
3.3.2 圓柱運動軌跡變化---------------------------------------33
3.4 均勻流場中彈性雙圓柱之運動模式探討-------------------35
3.4.1 並列固定雙圓柱之流場特性分析---------------------36
3.4.2 並列彈性雙圓柱之運動模式探討---------------------38
3.4.3 縱列固定雙圓柱之流場特性分析---------------------39
3.4.4 縱列彈性雙圓柱之運動模式探討---------------------42
3.5 剪切流場中彈性雙圓柱之運動模式探討-------------------43
3.5.1 剪切參數對並列雙圓柱之運動模式的影響---------43
3.5.2 剪切參數對縱列雙圓柱之運動模式的影響---------45
第四章 結論與建議------------------------------------------------------------47
參考文獻-------------------------------------------------------------------50

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