Numerical Analysis of Two-Dimensional Gas Flow in Micro-Step-Channels

• Main Authors: Chih-Neng Hsu, 許智能
• Other Authors: Shwin-Chung Wong
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/23726142469194386677

碩士 === 國立清華大學 === 動力機械工程學系 === 88 === Direct Simulation Monte Carlo (DSMC) method is adopted to explore the distribution of velocity,temperature, pressure ,and density of two dimensional micro backward/forward facing step channels from slip flow to free molecular flow conditions. Compressibility and rarefaction are also discussed in the thesis. Calculations are performed at the step heights of 0.5micro -m, 1micro-m, and 1.5micro-m with outlet Knudsen number (Kne) ranging from 0.05 to 100. The channel length is 2micro-m and the pressure ratio of inlet and outlet region is set to be 3. The result indicates that the low pressure circulation region behind the backward facing step of heights 0.5micro-m,1micro-m ,and 1.5micro-m disappears as Kne is larger than 1.3,2.3,and 4 , respectively. However, for forward facing step channels, a little markedly circulation occurs before it. Temperature is not constant in the micro backward/forward facing step channels. When the pressure gradient is large,the pressure is not linearly dropped and the temperature decreases markedly along the channel. When the gas is more rarefied, namely, Kne is large,the pressure tends to decrease linearly ,the temperature drop becomes small, and the slip velocity on the wall increases.