|其他題名: ||The investigation of fluid dynamics and heat transfer of micro-channel flows using DSMC simulation|
|作者: ||潘穎哲;Pan, Ying-jhe|
|上傳時間: ||2010-01-11 06:20:53 (UTC+8)|
|摘要: ||近年來由於工業的發展及半導體工業的成熟，相關領域的產品與物件都具有低成本、高精確度與運作快速等特性。微機電系統(Micro-Electro-Mechanical Systems, MEMS)的尺寸都與分子平均自由徑同等級甚至更小。在稀薄度氣體流場得分析中數值模型須考慮分子觀點。直接模擬蒙地卡羅(Direct simulation Monte Carlo, DSMC)法是目前被認為較精確且使用最廣泛的方法。 |
Due to the development and maturation of the semiconductor industry in recent year, the products of related fields are low-cost, high-accurate and high-speed. The characteristic size of Micro-Electro-Mechanical Systems (MEMS) is in the same order as or even smaller than the mean free path (MFP) of gas molecules. In rarefied-gas flow, a mathematical model, which bases on the molecular point of view, has to be considered in the predictions of flow dynamics. The direct simulation Monte Carlo (DSMC) method is a popular and accurate simulation technique for rarefied-gas flows.
In this thesis, the DSMC method was applied to analyze microchannels which are the most important elements of MEMS. At first, we simulate a 2-D straight rectangular cross-section microchannel using the DSMC method. To study the influence of rarefaction effects on the flow properties, the DSMC results are compared with the numerical solutions of Navier-Stokes equations with slip boundary conditions. The discrepancy between the DSMC results and the Navier-Stokes solutions becomes more obvious when the degree of rarefaction increases. The results show that we must use the DSMC method in rarefied-gas flows to get more accurate results.
In order to reduce the computation time and memory requirement, the 2-D simplification of a 3-D flow problem is often used in the DSMC simulation. In practical engineering applications, this simplification, however, is inappropriate as the cross-section aspect ratio of the 3-D structure decreases. We simulated the 3-D straight rectangular cross-section microchannels, the 3-D microchannels with microstructures and the 3-D microchannels with backward-facing steps. The results of the 3-D structures are compared with those of 2-D simplifications. It is found that the approaching level of the 3-D results to those of the 2-D simplification is over 98 % when the cross-section aspect ratio is greater than 5. When the cross aspect ratio is less than 5, the influence of 3-D effect can no longer be ignored and it is necessary to use a full 3-D simulation in the analysis of microchannel flows.