臺灣博碩士論文加值系統

本研究以二維環狀剪力槽作為實驗儀器，藉由內外邊壁轉動，施予槽內顆粒體剪切力及能量，並使用高速攝影機與數位攝影機，進行分析及觀察記錄顆粒體群聚現象，由實驗結果發現，當群聚現象發生時，群聚顆粒的流場切線速度會趨近於零，粒子溫度會下降。當末轉速上升時，粒子群聚強度下降。當系統顆粒總數增加時，粒子群聚強度會變大，且在高轉速時，增加的顆粒數對於群聚強度有較明顯的變化。另外當末轉速上升時，群聚團的粒子溫度與平均動能也隨之上升，顆粒團擾動較大，越不容易群聚。降低末轉速與增加顆粒總數，顆粒群聚時間會相對縮短。此外，我們也發現，在低轉速下，群聚密度較為緊密，且隨著末轉速上升，群聚的外型長寬比漸小，但當增加顆粒總數時，長寬比會隨之上升。我們也發現群聚密度與粒子溫度呈現Power law的關係，且粒子溫度與群聚強度也呈現Power law的關係，而群聚長寬比與群聚強度則呈現線性關係。在最後我們由實驗的結果歸納出不同轉速與顆粒總數下，群聚與未群聚之相圖，利用相圖便可以清楚瞭解各條件下顆粒是否產生群聚現象。

The kinetic energy of particles is dissipated because of the inelastic collisions and friction effect. Hence, granular materials has an interesting phenomenon that the so-called granular clustering. In this study, we performed a series of experiments to investigate the phenomenon of granular clustering by using two-dimensional annular shear cell. The particle motions are recorded by a high-speed camera and a digital camera. Image processing technology and particle tracking method are employed to measure the velocities, local solid fraction, clustering particle number and granular temperature. The results show that the tangential velocity is closed to zero, and the granular temperature is also reduced. The cluster index increases with the decrease of the final outer wall velocity and the increase of the particle number of system. The particle number of system has a significant influence on cluster index as the higher final wall velocity is applied. The particle cluster is not easy to form with the higher final wall velocity leading to the greater granular temperature. The clustering time is reduced with the decrease of final wall velocity and the increase of particle number of system. The cluster density and cluster aspect ratio increase as the final wall velocity is reduced. Additionally, we demonstrate that cluster density and granular temperature exists a power law relationship and granular temperature and index of cluster also show the power law relationship. Finally, the phase diagram of cluster is found according to the final wall velocity and the particle number of system.

附表目錄 V
附圖目錄 VI
符號說明 IX
第一章 緒論 1
1.1粒子流簡介 1
1.1.1顆粒體 1
1.1.2 粒子流特性 2
1.2 剪力粒子流研究發展 4
1.3 顆粒氣體群聚現象 5
1.4 研究動機與架構 9
第二章 實驗方法與原理 11
2.1 實驗設備 11
2.1.1 二維環狀剪力槽 11
2.1.2 顆粒體 12
2.1.3 觀測及量測儀器 13
2.2 實驗方法及原理 15
2.2.1 粒子溫度概念 15
2.2.2 影像處理分析方法 16
2.2.3 分析參數 18
2.3 實驗流程及步驟 19
2.3.1 實驗配置 19
2.3.2 實驗步驟 20
2.4 實驗誤差 22
第三章 結果與討論 24
3.1顆粒群聚現象 24
3.1.1顆粒群聚現象之觀察 24
3.1.2影響顆粒群聚的因素 26
3.1.3顆粒群聚性質探討 27
3.1.4顆粒群聚與未群聚之差異 28
3.2不同末轉速與顆粒數對顆粒群聚現象之影響 29
3.2.1 群聚強度與外環末轉速之關係 30
3.2.2 群聚粒子溫度、群聚粒子動能與不同外環末轉速之關係 32
3.2.3 群聚時間對不同外環末轉速之關係 33
3.3顆粒群聚密度與群聚形狀之探討 34
3.3.1 顆粒群聚密度 34
3.3.2 群聚形狀 35
3.3.3 粒子溫度、群聚密度、群聚強度與群聚長寬比之關係 36
3.3.4 顆粒群聚條件之相圖 38
第四章 結論 39
參考文獻 40
附錄 44

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