https://scholars.lib.ntu.edu.tw/handle/123456789/80816
標題: | 聲波引致懸浮微粒聚結的理論研究及數值計算(1/2) Theoretical and numerical study of acoustic coagulation of suspended particles |
作者: | 李雨 | 關鍵字: | 微粒聚結;次微米微粒;聲波;布朗擴散;質量守恆;coagulation of small particles;sub-micron particles;sound wave;Brownain diffusion;mass conservation | 公開日期: | 31-七月-2002 | 出版社: | 臺北市:國立臺灣大學應用力學研究所 | 摘要: | 本計劃以數值計算方法研究二相懸浮流中的微粒聚結問題,本文完成之工作有三:(1)以正動力作用(orthokinetic interaction)模式進行聲波聚結的數值模擬,並與多項前人實驗作詳細的比較驗證,結果顯示我們需要採用甚低的碰撞效率係數(約0.2 – 0.4,視不同條件參數而定)方可使數值計算與實驗結果相吻合。(2)就次微米微粒,我們比較了布朗聚結與聲波聚結的效率,前者隨著粒徑之下降而上升,後者則反之,就一般條件下的數值模擬結果而言,50奈米以上的微粒也可採用聲波效應加速聚結。(3)就正動力作用模式、流力作用(hydrodynamic interaction) 模式,及綜合二者的聲波尾跡(acoustic wake) 模式,本文均進行了聲波聚結的數值模擬,結果顯示隨正動力作用模式外,其餘模式均不能維持質量守恆。上述(1)及(3)兩項顯示目前的碰撞頻率函數理論模式並不完備,且數值方法亦有進一步研究的必要,而是下年度主要的研究工作。 This project studies numerically the coagulation of small particles in a two-phase suspension flow. Three topics have been completed in the present project. (1) We have validated our calculations by comparing with different previous experiments using the orthokinetic interaction model for the collision frequency function. It is found that a relative low value of collision efficiency factor (about 0.2 – 0.4, depending on different parameters) is required for a correct numerical prediction. (2) For the coagulation of sub-micron particles, we have studied in details the relative importance of the Brownian coagulation and the acoustic coagulation. The effect of the Brownian coagulation increases as the size of the particle increases, but is opposite for the acoustic coagulation. For general cases, it is found that the acoustic effect can aid the coagulation when the diameter of the particle exceeds 50 nm. (3) We have carried out simulation of acoustic coagulation using the orthokinetic interaction model, the hydrodynamic interaction model, and the acoustic wake model (a combination of orthokinetic and hydrodynamic model). It is found that only the simulation with orthokinetic interaction model can preserve the mass of particles during the calculation. The items (1) and (3) stated above indicate that both the theory of the collision frequency function and the numerical method require further investigation, and will be studied in the second year. |
URI: | http://ntur.lib.ntu.edu.tw//handle/246246/21645 | 其他識別: | 902212E002199 | Rights: | 國立臺灣大學應用力學研究所 |
顯示於: | 應用力學研究所 |
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902212E002199.pdf | 205.76 kB | Adobe PDF | 檢視/開啟 |
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