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.
