Computation of Gaseous Flows in Microchannel

• Main Authors: Chen-yu Hwang, 黃振彧
• Other Authors: Chii-Jong Hwang
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/98579110067504277835

碩士 === 國立成功大學 === 航空太空工程學系碩博士班 === 95 === In the last decade, the microelectromechanical system(MEMS) field has significant and impressive progress. For the microchannel flows, a lot of experimental and theoretical results have been presented, but it still exists some problems which are worthwhile to study. In this thesis, the numerical computations are performed to investigate the gaseous flow behaviors in the microchannels. First the unstructured tetrahedral and prismatic meshes are created in the flow domain, the four-step Runge-Kutta time integration scheme and finite volume upwind method are adopted to solve the unsteady three-dimensional Navier-Stokes equations in he Cartesian coordinate system. To efficiently treat the geometric problem, the CATIA software is introduced to generate geometric shape, surface triangular grids and prismatic meshes. Then the mesh generation technique presented by Liu and Hwange is utilized to finish the distribution of tetrahedrons. To investigate the low speed flows, the approach for solving the pressure, which was presented by Rossow, is adopted in this study. On the unstructured tetrahedral/prismatic meshes, the above approach is extended to solve the three-dimensional inviscid and laminar flow. To evaluate this numerical method, the inviscid flows around sphere and passing through the converging-diverging nozzle with circular crosssection are investigated first. For the different Mach number, the comparision between the computed pressure coefficient and velocity distributions on the surface of sphere and the results from the potential flow theory is performed. Also the history of convergence is studied. About the nozzle flow, the pressure and velocity distributions along the nozzle axis are compared with those from the isentropic flow. Secondly, the computation of pipe flow is processed. For the comparision between the present results and the analytical solution for the poiseuille flow (such as entrance length and poiseuille number), the accuracy of current numerical approach for solving the laminar flow is confirmed. Finally, the present solution procedure is applied to study the trapezoidal microchannel. For the different value of Knudsen number and Mach number, the distribution of Poiseuille number and pressure distribution are computed and compared with the related data in the other literature.