剪力流中分離現象研究

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Title:	剪力流中分離現象研究
Authors:	黃俊豪;Chung-Hao Huang
Contributors:	機械工程研究所
Date:	2006-07-07
Issue Date:	2009-09-21 11:54:44 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本文觀察經剪力作用之混合大小粒子並探討其分離現象，普遍認為由粒徑差異所造成的分離現象主要由滲透效應來主導，所謂的滲透效應即小粒子藉由外來能量而穿透大粒子間隙的一種遷移現象。本文使用實驗方法，針對底盤速度與粒子佔有體積比對粒子在剪力槽內分離現象所造成影響做探討。藉由觀察剪力槽內分離現象隨時間變化情形，分析小粒子之速度分布以及粒子溫度、濃度分佈、分離強度等，實驗發現底盤速度與粒子佔有體積比提高，粒子之平均速度梯度、x 方向與y 方向擾動速度梯度以及粒子溫度梯度皆會增加，且高底盤速度與高粒子佔有體積亦具有較大初始分離速率與穩定狀態時較高之分離強度值，其中粒子佔有體積比對初始分離率與最大分離強度具有較大的影響力。另外亦針對粒徑比，利用剪力槽上壁面所裝置三個雙向應力規來量測剪應力與正向應力，分析作用於剪力槽邊壁之應力大小。 This thesis examines the segregation phenomena of binary granular material subjected to external sheared force. This type of flow in a shear cell is known as Couette flow in fluid mechanics. The influence of both the bottom wall velocity and solid fraction of granular material on the segregation behaviors are discussed.Experiments are performed in a shear cell device and the glass spheres are used as granular materials. The motions of the granular materials are recorded by a high-speed camera. Image processing technology and particle tracking method are employed to measure the average and fluctuation velocities in the streamwise and the transverse directions. Two models are used to describe segregation level and an index called intensity of segregation, Is, is employed to quantify the segregation quality. The initial segregation rate is calculated from a least-square fit using the time evolution of Is. Three bi-directional stress gages are installed on the upper wall to measure the nomal and shear stresses.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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