臺灣博碩士論文加值系統

本文以直接模擬蒙地卡羅法(Direct Simulation Monte Carlo Method)[1]來模擬三維矩形微管之低流速流場，並比較二維流場與三維流場模擬之差異性；另外，固定出入口壓力比為2.5，以改變三種不同入口壓力，來改變其紐森數，藉以觀察不同紐森數區間，對流場性質之影響；另外還要觀察不同壁溫對流場的影響，本文所使用的工作流體為氮氣(N2)，分子模型則採用VHS分子模型。
模擬之結果發現，三維之模擬結果與二維之模擬結果有明顯的差異；就速度分佈來看，三維流場之模擬結果比二維流場之模擬結果低了許多，大約只有二維模擬的65％，這是因為三維模擬流場之管壁效應比二維模擬流場大的結果。另外比較三個不同入口壓力之算例，我們可以發現隨著流場稀薄度的增加，其邊界滑移速度會變大；但是流場內部之速度分佈則是隨著紐森數的增加而減小。另外，在熱通量的分析上，三維流場之模擬結果比二維流場之模擬結果，更早達到流場與壁面成熱通量平衡的狀態，而紐森數高的流場其熱傳之現象比較不明顯。

In this paper, the direct simulation Monte Carlo has been applied to compute 3-D Low-speed Micro-channel Flows, then compare with the difference in 2-D and 3-D flows. Variation of the Knudsen number is obtained by change the inlet pressure while keeping the pressure ratio. The effects of varying Knudsen number on flow property were investigated. The VHS model and Nitrogen has been applied.
The result shows that simulation of 3-D differs a lot from 2-D. In the velocity distribution, the result of the 3-D is lower than 2-D,about only 65% of 2-D,because the friction of the wall. In addition, compare to the different inlet pressure case, wall slip velocity increase and inner velocity decrease along the enhanced rarefaction. On the analysis of heat flux, the result of 3-D is larger then 2-D, but not distinct with high Knudsen number.

目錄............................................I
表目錄........................................III
圖目錄.........................................IV
符號說明.......................................VI
第一章 緒 論...................................1
1-1 前言........................................1
1-2 紐森數的定義................................4
1-3 波茲曼方程式及其解法........................5
第二章 直接模擬蒙地卡羅法......................10
2-1 DSMC 法....................................10
2-2 網格設置與計算時步.........................12
2-3 流場初始狀態...............................12
2-4 流場邊界處理...............................14
2-5 低速流之進出口條件設定方法.................16
2-6 碰撞對(Collision Pair)的選擇...............18
第三章 分子模型的選擇..........................20
3-1 分子模型...................................20
3-2 VHS分子模型................................20
3-3 單原子分子模型.............................21
3-4 雙原子分子模型.............................23
第四章 結果與討論..............................26
4-1 二維與三維模擬結果之比較...................26
4-2 不同入口壓力對流場的影響...................29
4-3 不同管壁溫度對流場的影響...................31
第五章 結論與未來工作..........................33
5-1 結論.......................................33
5-2 未來工作...................................34
參考文獻.......................................35

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