직접모사법을 이용한 형상 변화에 따른 미소채널 유동 해석

Abstract

In the present study, to investigate the characteristics of subsonic rarefied gas flows in micro-channels with shape change, flow simulations of micro-channels with different geometries were conducted using a direct simulation Monte-Carlo (DSMC) solver based on unstructured meshes. For simulating micro-channel flows like pressure driven flows, the pressure boundary conditions at the inlet and the exit were additionally applied. Verification of the boundary condition was conducted by comparing with other researchers’ DSMC simulations with the pressure boundary condition. After verification of the boundary condition, the straight micro-channel of 15μm × 1μm was considered for the baseline channel. The pressure conditions at the inlet and the exit were 5×105 Pa and 1.66×105 Pa, respectively. The inlet gas temperature and wall temperature were both 300K, and a fully diffuse reflecting wall was considered. Three types of change of shapes were considered. The change of the length, height and bend angles were treated for this study. Firstly, to investigate the effects of the change of length, half and twice of the baseline channel length were considered. It was shown that the pressure gradient was dominantly affected by the change of the lengths. As a result, the velocity was more accelerated for short length channel than for the baseline channel. On the other hand, when the heights were become higher, the changes of flow properties were greater than the baseline channel due to the area of boundary layers or the forces by the pressure gradient. Finally, the effects of the bend angles in micro-channels were investigated with several bend angles. The angles were considered from 0 to 135 degrees. When the angle became greater, the flow separation was generated at the concave type corner. For larger angles, the variation of flow properties at the corner became greater. Flow properties at the exit were different trend from those at the corner. Pressure and density at the exit were not dependent on the bend angles, whereas the velocity at the exit was increased according to the bend angles.