圓片顆粒體在振動床迴流現象之研究-電腦模擬與實驗之驗證

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题名:	圓片顆粒體在振動床迴流現象之研究-電腦模擬與實驗之驗證
作者:	黃信誠;Huang,Sin-Cheng
贡献者:	機械工程學系
关键词:	圓片顆粒體;振動床實驗;離散元素法;實驗驗證;傳輸性質;剪力帶分佈;Disk particulate;Vibrated bed;DEM;Experimental Validation;Transport properties;Shear band
日期:	2015-11-09
上传时间:	2016-01-05 18:34:24 (UTC+8)
出版者:	國立中央大學
摘要:	研究使用離散元素法(DEM)模擬圓片顆粒體在振動床中的迴流現象，探討背景阻尼對振動床系統的影響，並以實驗結果驗證DEM模擬的結果。實驗採用改良式粒子追蹤法(Improved Particle Tracking Velocimetry)量測圓片顆粒體的平移速度及旋轉速度，進而計算顆粒體傳輸性質(例如：局部平均速度、局部擾動速度、局部粒子溫度、擾動速度分佈、擴散係數與整體平均動能)。由實驗結果得知兩側顆粒體旋轉速度在振動床中頗為顯著。在DEM模擬所需要的圓片重要輸入參數，皆由基本測試量測而得。本研究比對實驗結果與DEM模擬結果，發現DEM沒有加背景阻尼的系統能量甚大於實驗系統的能量，而DEM加入背景阻尼的結果有效地消散模擬系統過大的能量，並與實驗的傳輸性質吻合。最後使用驗證合理的DEM模擬結果，分析顆粒體在振動床的內部性質，結果證實振動床兩側與底部剪力帶確實存在，而在剪力帶區域裡，其剪率(shear rate)較大。另外，發現振動床中間部分顆粒個數與接觸頻率較多，但接觸力道與平均旋轉速度較小，而振動床兩側顆粒個數與接觸頻率較少，但接觸力道與平均旋轉速度較大。;This paper proposes a discrete element method (DEM) model to simulate the convection phenomenon of circular disk particles in a vibrating bed. The effect of background damping on the convection behavior of disks was investigated. The discrete element simulations were validated with the corresponding experiments. The improved Particle Tracking Velocimetry (PTV) was employed to measure translational and rotational velocities of these disk particles in the vibrating bed. The transport properties of disk particles (such as local average velocities, local fluctuation velocities, local granular temperature distributions, fluctuation velocity distributions, and self-diffusion coefficients) in the vibrating bed were evaluated from the experimental results. The results showed that the average rotational velocities of disk particles adjacent to the sidewalls can play a significant role in a vibrated granular bed. The important particle properties required for DEM simulation were not simply assumed but measured directly in laboratory tests. The corresponding transport properties from DEM results were also analyzed. The comparison between the DEM results and experimental results was made and discussed in this paper. It can be seen that the system energy is larger in the DEM results without background damping than in the experimental results. However, the DEM results with background damping matched well with the experimental results. The internal characteristics in the vibrating bed were further analyzed via a reasonably validated DEM model. The DEM　results corroborated that the shear bands occur at the regions neighboring the sidewalls and the bottom base. In addition, although the solid fraction and contact frequency are larger in the central part of vibrating bed, the contact forces and particle rotational velocities are smaller. In contrast, although the solid fraction and contact frequency are smaller in the regions neighboring the sidewalls, the contact forces and particle rotational velocities are larger.
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