Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/2263
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dc.contributor.advisor陳志敏zh_TW
dc.contributor.advisorJerry M. Chenen_US
dc.contributor.author呂邦超zh_TW
dc.contributor.authorLu, Pang-Chaoen_US
dc.date2001zh_TW
dc.date.accessioned2014-06-05T11:42:48Z-
dc.date.available2014-06-05T11:42:48Z-
dc.identifier.urihttp://hdl.handle.net/11455/2263-
dc.description.abstract本文以實驗量測探討縱列雙圓柱尾流渦漩剝離的特性及互鎖的現象。實驗主要是量測尾流渦漩剝離頻率、表面壓力、阻力、雙穩定現象、及尾流渦漩結構,並利用煙線可視化技巧,來觀察近尾流場的結構。 實驗是在開放式風洞中進行,測試模型為直徑20-60mm之圓柱,雷諾數範圍為4500-15000之間。首先針對靜態縱列雙柱體研究,結果發現,渦漩剝離頻率與雙柱體無因次間距(L/D)有密切的關係。在臨界間距(L/D=3.88-4.22)時,有兩個頻率交替發生,此時流場的特徵為存在兩種穩定狀態的狀況,稱為雙穩定流場。在臨界間距下利用頻譜分析得知,高頻部分是由上游柱體形成的渦漩造成,低頻部分則是由下游柱體形成的渦漩造成。雙頻交替的產生並無週期性。 動態的探討上除了與靜態量測相同外,藉由改變上游柱體之震盪頻率及震盪振幅,探討在不同震盪模式下流場發生鎖定現象與臨界間距的關係。結果發現,不同間距所對應的鎖定邊界,隨著間距的增加,逐漸往右邊移動,接近單一柱體鎖定邊界。另外針對不同震盪頻率仍可找到適當的振幅,使得流場仍有雙穩定現象的產生。 比較本文中靜態與動態縱列雙柱體的研究結果,對於縱列雙柱體之雙穩定現象現象及渦漩剝離機制可以有更進一步的了解。zh_TW
dc.description.abstractThe vortex shedding for two identical circular cylinders in a tandem arrangement have been studied experimentally. The experiments were performed in an open-type wind tunnel for Reynolds number raging from 4500-15000. In addition to the case of two stationary cylinders, the oscillating case involves a rotationally oscillating upstream cylinder. The vortex shedding frequency, lock-on regime, surface pressures, drag forces, and vortical structure of the near wake are described. At the critical spacing where the dual vortex shedding frequencies take place have been observed for the stationary case well as for the oscillating case. The occurrence of dual shedding frequencies indicates switching of the flow patterns between two stable states and is referred to as the bistable flow. Moreover, the two shedding frequencies appeared intermittently, in which the lower frequency results from the vortex shedding behind the downstream cylinder and the higher frequency from the upstream cylinder. In the oscillating case, research is emphasized on the control of the bistable flow. This is attained by rotationally oscillating the upstream cylinder while holding the downstream cylinder stationary. The vortex shedding from a rotationally oscillating cylinder is found to lock-on to the external forcing at certain oscillation frequency and amplitude. As the spacing between the cylinders is increased, the lock-on boundary moves toward higher frequencies, and progressively close to that for a single oscillating cylinder. The bistable flow could also occur when the vortex shedding is locked-on to the oscillating upstream cylinder. The effects due to vortex lock-on and bistable shedding are reported and discussed in detail.en_US
dc.description.tableofcontents目錄 III 中文摘要 I 英文摘要 II 圖目錄 VI 符號說明 X 第一章 緒論 1 1-1 研究動機 1 1-2 文獻回顧 2 1-3 研究目的與本文組織 5 第二章 實驗設備 7 2-1 風洞 7 2-2 模型 7 2-3 動態驅動機構 7 2-4 量測設備及訊號擷取系統 9 2-5 流場可視化設備 9 第三章 實驗方法及程序 14 3-1 實驗參數 14 3-2 儀器校驗 14 3-2.1 風速校驗 14 3-2.2 流場速度量測儀器較驗 15 3-2.3 壓力量測儀器較驗 15 3-3 量測方法 16 3-3.1 尾流頻譜量測及互所的判定 16 3-3.2 渦漩形成長度的量測 16 3-3.3 表面壓力的量測 17 3-3.4 相位差量測 17 3-3.5 頻率解析度的計算方法 17 3-4 準確度的探討討 18 第四章 實驗結果 — 靜態縱列雙圓柱 21 4-1 渦漩剝離頻率 21 4-2 表面壓力及阻力量測 28 4-2.1 表面壓力量測 28 4-2.2 阻力量測 31 4-3 渦漩形成長度與臨界間距 33 4-4 流場可視化 35 4-5 阻塞效應 39 4-5.1 阻塞率校驗 39 4-5.2 不同模型尺寸雙穩定流場比較 40 第五章 實驗結果 — 震盪縱列雙圓柱 44 5-1 鎖定行徑與邊界 45 5-1.1 鎖定行徑 48 5-1.2 L/D=3鎖定邊界 50 5-1.3 L/D=2鎖定邊界 54 5-1.4 L/D=4、5鎖定邊界 57 5-2 流場鎖定邊界 57 5-3 表面壓力及阻力量測 69 5-3.1 表面壓力量測 69 5-3.2 阻力量測 72 5-3.3 表面擾動壓力 74 5-4 渦漩形成長度 78 5-5 流場可視化 80 第六章 實驗結果 — 二維效應 86 6-1 單一圓柱二維效應 86 6-2 雙圓柱二維效應 89 第七章 結論與建議 92 附圖 95 參考文獻 97zh_TW
dc.language.isoen_USzh_TW
dc.publisher機械工程學系zh_TW
dc.subjectbistableen_US
dc.subject雙穩定zh_TW
dc.subjectcritical spacingen_US
dc.subjecttandem arrangement cylindersen_US
dc.subjectlock-on boundaryen_US
dc.subject臨界間距zh_TW
dc.subject縱列雙圓柱zh_TW
dc.subject鎖定邊界zh_TW
dc.title靜態與震盪縱列雙圓柱之流場實驗研究zh_TW
dc.titleExperimental Study of Stationary and Oscillating Circular Cylinders in a Tandem Arrangementen_US
dc.typeThesis and Dissertationzh_TW
item.fulltextno fulltext-
item.languageiso639-1en_US-
item.openairetypeThesis and Dissertation-
item.cerifentitytypePublications-
item.openairecristypehttp://purl.org/coar/resource_type/c_18cf-
item.grantfulltextnone-
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