| 摘要: | 顆粒體在日常生活中是四處可見的，諸如：食鹽，糖，咖啡，粉末，沙和煤等等。 顆粒體雖然也是由普通的物質所構成的，但是在某些方面顆粒體的行為與一般的氣體，液體或固體的性質完全不同。在這篇論文，我們主要是分別在實驗和理論上探討顆粒體複的雜流動現象。 在最近幾年，顆粒體分離現象被發現在二維旋轉圓盤和三維旋轉柱體之中。在第二章中 ，我們建構了一個二維的模型來研究在二維圓盤中的分離現象。我們考慮顆粒體置放在一個繞著中心點選轉的二維晶格之中。 而主要的假設是在表層的顆粒會產生崩塌, 而在顆粒內層中的運動是伴隨著圓盤轉動 。 事實上許多工廠利用振動粉末來當作一個製造的過程。最近, 許多顆粒體在垂直地顫動的研究是十分地任人感興趣。而沙堆形成是在顫動的系統的模式形成之一。在第三章，我們描述動態堆形成並且也建構了一個模型。成功的描述了振動時的堆積過程。 在河邊和高山，常常可以發現山崩的發生。然而不管山崩的實際的重要性，但是我們對這些山崩的性質卻並不是十分瞭解。所以在第四章中，我們針對山崩問題做了一系列的研究，藉以試圖瞭解山崩的性質。 我們發現在崩塌的過程中可以發現有2 個特徵的角度來描述一崩潰的形狀。 Granular materials are very common in everyday life: salt, sugar, coffee, powder, sand and coal etc . They are made of common substances but in some way their behavior is completely different from what we can see in homogeneous gases, liquids or solids. In this thesis, we report on both experimental and theoretical investigation of flow of granular materials. Recently, the phenomenon of particle segregation was found in both two dimensional rotating drum and three dimensional rotating cylinder. In Chapter 2, "FRICTION-INDUCED SEGREGATION", we propose a model of two dimensional rotating drum which reproduces the phenomenon of radial segregation. It is a simple algorithm for simulation of rotating drum. We considered a rectangular lattice forming bands moving around central point. The main assumption is that the system takes place in the avalanches at the surface, whereas the motion of the grains in the bulk are equally adverted by the bulk flow. In fact many practical industrial situations involve the vibration of powders and granulates as an important part of a fabrication process. Recently, many attentions are focused on the study of granular materials lying on a vertically vibrating surface. The heap formation is one of pattern formations in the vibrating system. In Chapter 3, "HEAP FORMATION IN VERTICALLY VIBRATING GRAINS", we describe dynamic of heap formation and also construct a model to simulate heap formation using cellular automata. In the landslide close to rivers, the collapses of nearby slopes are mainly due to the versions of the river bed. Despite the practical importance of these avalanches, very little is known about the properties of these avalanches. In Chapter 4, "AVALANCHES FROM A COLLAPSING GRANULAR PILE", we report of an experimental investigation of the statistical properties of these type of avalanches. It is found that two angles of repose are needed to describe the shape of a collapsing granular pile. |
