臺灣博碩士論文加值系統

本研究針對圓盤在靜止流體中等速移動，在不同的速度條件下，使用實驗方法研究圓盤周圍的流場特徵模態。圓盤的直徑與厚度分別為60 mm、90mm及厚度1mm，利用線性馬達驅動移動機構，使得圓盤在靜止流體中形成等速移動，並調整移動速度。實驗中的圓盤雷諾數介於240與6000之間。使用質點軌跡視流法記錄圓盤周圍的流場瞬時衍化照片，呈現圓盤周圍之縱切面上的流場特徵行為。根據流場特徵照片分析圓盤周圍的拓樸流場觀察。圓盤移動時，在尾流區域形成單環狀渦漩結構。針對流場的特徵行為，採用質點影像測速儀技術量化圓盤周圍的全域速度場，計算速度向量場、渦度分佈圖、速度分佈及剪應力分佈。在渦度分佈圖中，環狀渦漩的特徵是兩個轉向相反的渦度集中區域。在渦流環出現的區域附近，產生大的徑向速度。當環狀渦漩形成時，會產生最大剪應力。本研究探討圓盤雷諾數對渦漩結構尺寸、等渦度分佈、速度分佈特性及剪應力特性的影響。

Flow characteristics of a circular disk moving under a constant speed in quiescent fluid were experimentally investigated. The diameters of circular disk used in this study were 60 mm and 90 mm, respectively. The thickness of the circular disk was fixed at 1 mm. The circular disk was moved with a constant speed by a traversing machine driven by a linear motor. The Reynolds numbers adjusted by controlling the moving speed of the circular disk were within the ranges of 0 – 3050. The instantaneous flow images in the symmetry plane around the circular disk were recorded by laser-assisted particle flow visualization method. According the observation of flow patterns, a single annular vortex ring denotedby an annular vortex ring formed in downstream surface of the circular disk. The flow fields of the circular disk at various Reynolds number were quantified by particle image velocimetry. The velocity fields, vorticity contours, velocity distributions, and shear stress around the wall of the circular disk were determined. The vortex ring was characterized by two vorticity concentrated areas of opposite signs in the vorticity contour. The large velocity in radial direction was formed at around the area where the vortex ring appears. The maximum shear stress is induced when the annular vortex ring was evolved. The effect of Reynolds number on the vortical structures, vorticity contours, velocity distributions, and shear stresses were examined and discussed.

摘要...i
Abstract...ii
誌謝...iv
目錄...v
表目錄...viii
圖目錄...ix
符號索引...xxiii
第一章 緒論...1
1.1 研究動機...1
1.2 文獻回顧...1
1.2.1 圓盤於靜止流體中自由落下...1
1.2.2 圓盤於等速流體中...2
1.2.3 振盪圓盤在靜止流場中...3
1.3 研究目標...3
第二章 實驗設備、儀器與方法...4
2.1 實驗設備...4
2.2 實驗儀器...4
2.3實驗方法...5
2.3.1 流場可視化...5
2.3.2 質點影像速度儀...6
第三章 圓盤等速移動的流場衍化過程...8
3.1圓盤等速向上移動...8
3.2 圓盤等速向下移動...14
3.3 討論...20
第四章 平均速度場...22
4.1 平均速度向量場...22
4.1.1 圓盤向上等速移動...22
4.1.2 圓盤向下等速移動...28
4.2 渦度分析...33
4.2.1 圓盤向上等速移動...34
4.2.2 圓盤向下等速移動...40
4.3 討論...46
第五章 振盪圓盤的流場特徵...48
5.1 流場特徵衍化過程...48
5.2 流場特徵模態分區...51
第六章 結論與建議...52
6.1 結論...52
6.2 建議...53
參考文獻...180
Extended Abstract...182

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[24]作者:呂紹新,名稱:振盪圓盤於靜止流體中的流場特徵,出版者:雲林縣 :國立虎尾科技大學 , : 民109.06.,