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研究生:林昊勳
研究生(外文):Hao-Hsun Lin
論文名稱:顆粒外形對顆粒體在滑坡道流動行為之影響及內部性質之探討
指導教授:鍾雲吉
學位類別:碩士
校院名稱:國立中央大學
系所名稱:機械工程學系
學門:工程學門
學類:機械工程學類
論文種類:學術論文
論文出版年:2019
畢業學年度:108
語文別:中文
論文頁數:70
中文關鍵詞:離散元素法顆粒體崩塌傳輸性質內部性質摩擦啟動因子
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本研究使用離散元素法(Discrete Element Method, DEM)模擬三種質量相同但形狀不同(球形、雙球形及三球形)的顆粒體於一傾斜滑坡道自由崩塌之流動行為,並探討顆粒形狀對流動行為的影響,觀察三種顆粒體在滑動及沉積靜止時的外觀及其對應的物理性質。研究結果顯示球形顆粒體堆積高度較低且沉積的範圍較為廣泛,雙球形及三球形顆粒體堆積高度較高且較集中,顆粒間互鎖效應(interlocking effect)的強度依次為: 三球形顆粒體>雙球形顆粒體>>球形顆粒體。球形顆粒體在運動中易於滾動,整體運動速度較快,碰撞耗能比例較另外兩者更高,雙球形及三球形顆粒體外形較易互鎖,由摩擦主控著耗能及運動行為。雙球形及三球形顆粒體在運動過程中粒子體積佔有率及平均配位數較球形顆粒體大,而在沉積靜止時則是球形顆粒體較大。球形顆粒體在運動中的平均接觸力最大,而在沉積靜止時則為最小。研究結果進一步顯示顆粒體在運動過程中並非全然是滑動摩擦,同時也存在滾動摩擦。雙球形及三球形顆粒體接近滑動摩擦的比例皆較球形顆粒體高,數值最高的情況發生在三球形顆粒體中顆粒與牆壁的接觸,但也僅佔據約整體的70%。
The aim of this study is to investigate the gravity-driven free surface flow of granular avalanches over complex basal topography by using Discrete Element Method (DEM). Three different kinds of particle shape are used in the study, that is, spherical, double-spherical and triple-spherical. The influence of particle shape on the flow behavior is explored. Numerical results show that the particle interlocking effect follows the sequence: triple-spherical > double-spherical >> spherical. The spherical granules show a low packing height and a wide range of deposition, while the double-spherical and triple-spherical granules show a high packing height and a narrow range of deposition. The spherical granules intend to rotate during avalanche, move faster, and exhibit higher energy consumption from collision mechanism. The double-spherical and triple-spherical granules are easier to interlock, and the energy dissipation is mainly dominated by friction. The double-spherical and triple-spherical granules show higher solid fraction and coordination number during avalanche, while the spherical granules show more densely packed configuration at settlement. Not only sliding friction but also rolling friction occurs during avalanche. The percentage close to sliding friction of the double-spherical and triple-spherical granules is larger than that of spherical granules. Only 70% of particle-wall contacts in triple-spherical granules, the highest percentage, can attain sliding friction.
摘要 i
Abstract ii
目錄 iii
附表目錄 v
附圖目錄 vi
第一章 緒論 1
1-1 顆粒體的崩塌 1
1-2 顆粒體的崩塌實驗與模擬 1
1-3 崩塌過程的內部性質 4
1-4 研究動機 6
1-5 研究項目 6
第二章 研究方法 7
2-1 離散元素法 7
2-1-1 離散元素法之架構 7
2-1-2 三維剛體的運動方程式 7
2-1-3 接觸力模型 9
2-1-4 計算時間步 10
2-2 傳輸性質計算 10
2-2-1 能量計算 10
2-2-2 擾動速度 12
2-2-3 粒子溫度 13
2-3 內部性質計算 13
2-3-1 顆粒粒子體積佔有率 13
2-3-2 平均配位數 14
2-3-3 平均接觸力 14
2-4 摩擦啟動因子計算 14
2-4-1 摩擦啟動因子 14
2-5 離散元素模型 15
2-5-1 模型設立 15
2-5-2 顆粒體的自然沉積 16
2-5-3 顆粒體的崩塌滑動 16
第三章 結果與討論 17
3-1 顆粒體形狀對流動形態之影響 17
3-2 顆粒體形狀對傳輸性質之影響 18
3-3 顆粒體形狀對內部性質之影響 21
3-4 顆粒體形狀對摩擦啟動因子之影響 24
第四章 結論 28
參考文獻 30
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