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研究生:彭敏惠
研究生(外文):Min-Hui Peng
論文名稱:以HHT時頻分析法研究陣風風場中物體所受之風力
指導教授:朱佳仁朱佳仁引用關係
指導教授(外文):Chia-Ren Chu
學位類別:碩士
校院名稱:國立中央大學
系所名稱:土木工程研究所
學門:工程學門
學類:土木工程學類
論文出版年:2005
畢業學年度:93
語文別:中文
論文頁數:101
中文關鍵詞:希爾伯特-黃頻譜力平衡儀陣風風場風洞實驗
外文關鍵詞:Hilbert-Huang TransformForce BalanceGusty FlowWind Tunnel Experiment
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本研究以風洞實驗探討穩態風場和陣風風場中,三維矩柱、平板和模型樹所受風力之特性,實驗所使用的力平衡儀可以量測物體所受到的縱向力和側向力的瞬時變化。由實驗結果可以計算得物體的平均風力係數、風力係數之均方根和史徹荷數,矩柱的渦漩逸散頻率可由側向力資料經由以跨零點的方式計算得。本研究並採用希爾伯特-黃(HHT)的經驗模態分解法(Empirical Mode Decomposition, EMD)找出渦漩逸散的內建模態函數(Intrinsic Mode Function, IMF)分量,其結果和傅立葉頻譜所找出的渦散頻率比較,發現以上方法求得的矩柱在窄迎風面狀況下,史徹荷數都相當接近0.08,符合前人研究之穩態均勻流況的結果。陣風風場的實驗結果:阻力係數較穩態風場中為小,顯示紊流強度增強,阻力係數減小;矩柱在寬迎風面與窄迎風面狀況下之史徹荷數與穩態風場中接近。本研究之結果可以瞭解穩態風場與陣風風場中物體所受風力的影響,可提供相關工程參考。
This study experimentally investigates the wind force on three-dimensional rectangular prism, plate and tree model in a steady flow and periodically varying flows. The experiments were carried out in an atmospheric boundary layer wind tunnel. This wind tunnel is equipped with a gust generator that can generate periodically varying flows of adjustable frequency. The along wind force and cross wind force were measured by a high frequency force balance. Based on the force measurement, the mean drag, mean lift, rms drag, rms lift coefficients were calculated. The frequency of vortex shedding was determined by the method of cross-zero, Fourier spectrum and Hilbert-Huang Transform (HHT). The results agree with each other and previous studies in a steady flow. The drag coefficient decreases, the rms drag and lift increase under gusty flow. The Strouhal number is closed to those in a steady flow.
                     頁次
中文摘要                  i
英文摘要                 ii
目錄                   iii
圖目錄                  vi
表目錄                   x
符號表      xi
第一章 緒 論      1
 1.1 前言              1
 1.2 研究動機              1
 1.3 研究內容及大綱          2
第二章 理論基礎與文獻回顧          3
 2.1 流場之特性              3
 2.2 陣風之特性              3
 2.3 風流經物體之行為         4
 2.4 作用在物體的力         5
 2.5 頻譜分析              6
 2.5.1 傅立葉(Fourier)頻譜分析     6
 2.5.2 希爾伯特頻譜分析          8
 2.6 前人文獻回顧              10
第三章 實驗設備與方法          18
 3.1 大型環境風洞與陣風產生器     18
 3.1.1 大型環境風洞          18
 3.1.2 陣風產生器              19
 3.2 風速量測方法              20
 3.3 風力量測方法              22
 3.3.1 力平衡儀之描述          22
 3.3.2 力平衡儀之準確性校正     22
 3.4 實驗方法              23
 3.4.1 流場模擬             23
 3.4.2 模型              24
 3.4.3 實驗數據採樣技巧         24
 3.5 頻譜分析方法              25
 3.5.1 傅立葉(Fourier)頻譜分析     25
 3.5.2 希爾伯特-黃(Hilbert-Huang)頻譜分析 26
第四章 結果與討論               43
 4.1 陣風流場               43
 4.1.1 平均風速               43
 4.1.2 流場側方向的均勻性          43
 4.1.3紊流強度               43
 4.1.4 風速頻譜分析          44
 4.2 矩柱受風力之特性          44
 4.2.1 平均風力係數          44
 4.2.2 擾動風力係數          45
 4.2.3風力頻譜分析          46
 4.3 平板受風力之特性          48
 4.3.1平均風力係數          48
 4.3.2 擾動風力係數          48
 4.4 陣風風場中矩柱之HHT分析      49
 4.4.1 風攻角0˚之矩柱         49
 4.4.2 風攻角90˚之矩柱          50
 4.5 陣風風場中平板之分析          51
 4.6 模型樹在穩態風場與陣風風場之分析 52
第五章 結論與建議               96
 5.1 結論               96
 5.2 建議               97
參考文獻                   98
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