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題名 | Material Processing of Convection-Driven Flow Field and Temperature Distribution under Oblique Gravity=斜向重力加速度影響下對流主導材料處理之流體速度及溫度分怖 |
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作者 | 洪儒珍; 龍瀛天; | 書刊名 | Proceedings of the National Science Council : Part A, Physical Science and Engineering |
卷期 | 21:1 1997.01[民86.01] |
頁次 | 頁20-36 |
分類號 | 447.5 |
關鍵詞 | 斜向重力加速度; Material processing; Convection driven flow; Flow field; Temperature distribution; |
語文 | 英文(English) |
中文摘要 | 在法向及斜向重力加速度影響下,熱對流在極低壓下力,由原始材料經蒸汽沈澱 處理之數學模式作了研討:在法向重力加速度作用時,熱對流所推動的蒸汽沈澱可在複雜的 回流動模型下完成。在此種複雜的回流及非均勻溫度分佈的模型下,顯然無法達成處理均勻 精細的結晶狀薄膜。在斜向作用時,重力加速度可分解成垂直減弱加速度及水平分量加速度 。沿重力加速度垂直的剖面上可看出,減弱重力加速度可促進簡單向上流動及均勻溫度分佈 。此種流體運動及均勻溫度分佈可形成有利造成良好光學材料之晶體成長的環境。但因有水 平分量加速度的存在,總體上斜向重力加速度仍無法推動勻質晶體的成長。因此,要造成勻 質晶體成長的環境,恐怕仍有賴於在微重力太空環境下,來推動晶體的成長。 |
英文摘要 | A set of mathematical formulations is adopted to study vapor deposition from source materials driven by a heat transfer process under normal and oblique directions of gravitational acceleration with an extremely low pressure environment of 10 �� mmHg. A time step animation series of the initiation and development of flow and temperature profiles during the course of vapor deposition has been obtained through the numerical computation. Computations show that the process of vapor deposition is accomplished by the transfer of vapor though a fairly complicated flow pattern of recirculation under normal direction gravitational acceleration. It is obvious that there is no way to produce a homogeneous thin crystalline film with fine grains under such a complicated flow pattern of recirculation with a non-uniform temperature distribution under normal direction gravitational acceleration. There is no vapor deposition due to a stably stratified medium without convection for reverse normwal direction gravitational acceleration. Vapor deposition under oblique direction gravitational acceleration in the vertial direction is favorable for production of a homogeneous thin crystalline film. However, oblique direction gravitational acceleration also induces an unfavorable gravitational acceleration along the horizontal direction,which is responsible for initiation of a complicated flow pattern of recirculation. In other words, it will be necessary to carry out vapor deposition under a reduced gravity in future space shuttle experiments with an extremely low pressure environment so as to process vapor deposition with a homogeneous crystalline film with fine grains. Fluid mechanics simulation can be used as a tool to suggest the most optimistic experimental method with the best setup to achieve the goal of processing the best nonlinear optical materials. |
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