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    Title: 以CFD模擬二維斷面橋體氣動力特性研究
    Other Titles: Investigation on aerodynamic characteristics of 2D bridge sections by using CFD
    Authors: 吳唐綺;Wu, Tang-Chi
    Contributors: 淡江大學土木工程學系碩士班
    林堉溢;Lin, Yuh-Yi
    Keywords: section models;Bridge;CFD;FLUENT;Wind Engineering;計算流體力學;風力係數;橋梁
    Date: 2017
    Issue Date: 2018-08-03 14:57:56 (UTC+8)
    Abstract: 隨著時代的改變,在科技不斷進步的情況下,工程師也不斷挑戰橋梁跨度的極限,當橋梁跨徑不斷增加,柔度也會隨之變高,而風致結構反應的影響也會越來越嚴重。
    然而,橋梁風洞實驗是非常耗時、耗工的作業,因此,為能在進行風洞實驗前以分析方式粗估風致反應對橋梁所造成的影響,以便初步探討,本文採用計算流體力學(Computational Fluid Dynamics,CFD)進行橋梁風洞實驗分析以及模擬,取得氣動力參數。此方法無須風洞、模型以及儀器之建置成本,亦不受限於實際風洞之限制,既可減少實驗所消耗的時間,也可以分析風洞實驗無法實現之實際情況,如風速剖面、極高風速以及特定紊流……等特殊條件,再者,此方法也不受地點、地形以及氣候等自然環境影響,且相較於傳統風洞實驗,此法分析結果重複性相當高,可以不斷測試各種形式之橋梁斷面,以便取得完整資訊。
    計算流體力學分析雖然相對於風洞實驗而言是較為便利,但分析結果之正確性受輸入參數以及網格劃分技術之優劣影響甚深,因此,本文旨在探討如何建制良好的分析模式,透過CFD之運算,以求得良好的分析結果。
    本研究主要以數值分析為主,以過去風洞試驗的設置條件為基礎,模擬二維幾何斷面橋體在均勻來流下之風力係數,進行模擬風洞試驗的網格繪製、計算域配置以及邊界條件設定,再以ANASYS開發的計算流體力學套裝軟體FLUENT 15.0進行分析,最後將數值分析的結果與風洞試驗之風力係數比較,並討論不同設置條件以及不同網格繪製下的精準度,並針對其誤差做探討,進一步得到更適合橋樑斷面模擬的條件。
    本研究內容針對矩形斷面B/D=5、B/D=8、B/D=10以及B/D=13之風洞試驗進行數值分析比較,針對相同初始條件設置、不同網格繪製下之風力係數以及 進行探討,並依此設置為基礎進行風力係數與 之模擬、分析以此加以討論。
    Due to the rapid progress of computing efficiency, Computational Fluid Dynamics (CFD) has been proven to be more economical than the traditional wind tunnel tests. Therefore, this paper uses CFD to predict the aerodynamic coefficients of bridge deck cross sections. ANSYS FLUENT software is used to perform the simulations. The k-ω model is adopted to simulate the turbulence behavior of the flow field around the bridge section and speed distribution. And the aerodynamic coefficients are then obtained by the pressure. The rectangular cross-sections with the width-depth ratio ( B/D) of 5, 8, 10 and 13 are investigated. The attack angles ranged from 0-10 degrees are studied. The numerical results are compared with those obtained from wind tunnel tests. The comparison indicate that the results agree well at attack angles ranged from 0-6 degrees, however, the results are not consistent at attack angles larger than 6 degrees. This is because the 2D simulations are not suitable in these cases. The discrepancies can possibly be reduced by using 3D simulations in the future.
    Appears in Collections:[Graduate Institute & Department of Civil Engineering] Thesis

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