臺灣博碩士論文加值系統

本研究針對圓盤在靜止流體中往復振盪，在不同的振盪條件下，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及1mm，利用線性馬達驅動移動機構，使得圓盤形成周期性地往復振盪。藉由改變線性馬達的振盪速度與位移作為圓盤的振盪條件，改變實驗參數:分別為振盪圓盤的雷諾數及KC(Keulegan-Carpenter)數。實驗中的雷諾數介於0與2700之間，KC數介於0與1之間。使用質點軌跡視流法紀錄圓盤周圍的流場順時衍化照片，呈現圓盤周圍之橫切面與縱切面上的流場特徵行為。根據流場特徵照片分析振盪圓盤周圍的拓樸流場觀察，在雷諾數與KC數的域面上，振盪圓盤的流場特徵可畫分出四個模態—單環渦漩、雙環渦漩模態、過渡模態及單環渦漩逸放模態。單環渦漩模態時，在圓盤上游及下游皆形成單環狀渦漩。雙環渦漩時，圓盤上游及下游皆形成雙環渦漩。過渡模態時，圓盤上游形成單環渦漩，而在圓盤下游形成雙環渦漩;或是，在圓盤上游形成雙環渦漩，而在圓盤下游形成單環渦漩。單環渦漩逸放模態—在圓盤上游形成的單環渦漩往下游逸放。針對不同的流場特徵模態，採用質點影像測速儀技術量化振盪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。

Flow characteristics of an oscillating circular disk in quiescent fluid under various oscillating conditions were experimentally investigated. The diameter and thickness of the circular disk were 60 mm and 1 mm, respectively. A traversing machine driven by a linear motor was used to periodically oscillate the circular disk. The oscillating conditions including Reynolds number and KC (Keulegan-Carpenter) number were adjusted by controlling the moving speed and stroke of the oscillating circular disk. The Reynolds number and KC number were within the ranges of 0 – 2700 and 0 – 1, respectively. The instantaneous flow images in the symmetry plane and horizontal plane around the circular disk were examined by laser-assisted particle flow visualization method in a water tank. According the flow patterns four characteristic flow regimes are identified in the domain of Reynolds number and KC number: single annular vortex ring denoted by a annular vortex ring formed in upstream and downstream surfaces of the oscillating circular disk; dual annular vortex ring characterized two annular vortex rings evolved in the upstream and downstream surface of the oscillating circular disk; transition identified single annular vortex ring formed in upstream surface and dual annular vortex ring formed in downstream surface; single annular vortex ring shedding presented a single annular vortex evolved in upstream area and shed toward downstream. The phase-resolved ensemble-averaged flow fields of the oscillating circular disk at various characteristic flow modes were quantified by particle image velocimetry. The velocity vectors fields, vorticity contours, velocity distributions, and shear stress around the wall of the oscillating 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 is formed at around the area where the vortex ring appears. The maximum shear stress is induced when the annular vortex ring is evolved.

摘要.............i
Abstract........ii
誌謝.............iv
目錄..............v
表目錄...........viii
圖目錄...........ix
符號索引...........xxii
第一章 緒論...........1
1.1 研究動機...........1
1.2 文獻回顧...........1
1.2.1 圓盤於等速流體中...........1
1.2.2 圓盤於靜止流體中自由落下...........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 流場特徵...........7
3.1垂直平面...........7
3.2 流場特徵模態...........9
3.3 水平平面...........10
第四章 速度與向量...........13
4.1 垂直平面...........13
4.2 水平平面...........15
第五章 環狀渦漩特徵分析...........18
5.1 渦度分析...........18
5.1.1垂直平面...........18
5.1.2 水平平面...........20
5.2 尺度分析...........20
5.2.1 可視化...........21
5.2.2 PIV...........21
第六章 結論及建議...........23
6.1 結論...........23
6.2 建議...........25
參考文獻...........159
Extended Abstract...........161

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