剪力流中液體含量對混合機制的影響; Mxing mecanism in adherent shear flow

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Title:	剪力流中液體含量對混合機制的影響;Mxing mecanism in adherent shear flow
Authors:	周乘雨;Cheng-Yu Chou
Contributors:	機械工程研究所
Keywords:	顆粒流;剪力槽;粒子自我擴散係數;混合;Granular flow;Shear cell;Mixing;Diffusion
Date:	2005-07-01
Issue Date:	2009-09-21 11:50:54 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本文使用實驗方法，針對不同液體含量對粒子在剪力槽內之混合現象所造成之影響作探討。藉由改變液體含量來觀察顆粒體隨時間混合之過程，分析其混合層區域厚度 (Mixing Layer Thickness)、粒子擴散係數 (Particle Diffusion Coefficient)、混合區域內濃度分佈以及實驗數據與半理論模擬數據的比較，進而研究液體含量對混合層厚度的關係。在本文中，視擴散係數Dapp是一個重要的參數，代表流場混合快慢的指標，而這個參數也與液體含量、平均粒子溫度與剪率做比較，觀察其趨勢的變化。本實驗發現隨著液體含量的增加，平均速度、變動速度、視擴散係數與平均粒子溫度以及剪率都是下降的趨勢，說明了粒子間隨著液體含量的增加，其內聚力亦會增加，對其混合機制有減弱的影響。 The mixing and transport properties are influenced seriously by the amount of moisture added in the flow. If the particles are wet, the flow becomes more viscous and the liquid bridges and formed between particles. The dynamic liquid bridge forces are considered as the cohesive forces between particles to restrict the movements of particles. The cohesive forces make the particles stick tighter with each other and hamper the movement of particles. This paper discusses a series of experiments performed in a shear cell device with six different moisture contents and using 2-mm glass spheres as the granular materials. The motions of granular materials were recorded by a high-speed camera. Using the image processing technology and particle tracking method, the velocity, fluctuations and the granular temperatures were measured. The self-diffusion coefficient could be found from the history of the particle displacements. The mixing layer thicknesses were compared with the calculations from a simple diffusion equation using the data of self-diffusion coefficients obtained from the current measurements. The calculations and experimental results showed good agreements, demonstrating that the mixing process of granular materials occurred through the diffusion mechanism.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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