Direct simulation Monte Carlo (DSMC) in micro flows

Abstract

Researches on the micro flows in Micro Electrical Mechanical System (MEMS) have been an exciting field in the past few decades. Particle-based direct simulation Monte Carlo (DSMC) method can be applied to micro flows simulation in a wide Kn range. The objective of this thesis is to develop the DSMC algorithm and apply it to study micro flows. In present work, the algorithm of DSMC suitable for micro flows is developed with modified inlet and outlet boundary condition by means of particle control method and mass flux method. The scaling factor and the number of particles in each cell in DSMC have significant effects on the accuracy of results. Their effects are systematically studied in this thesis and the guidance was provided to ensure the accuracy and efficiency of the DSMC computations. Using the modified DSMC method, the 2-D micro channel flows are investigated and the axisymmetric micro tube flow is also studied by analytical method and compared with the DSMC results. Base on the database of DSMC computation, new slip velocity models suitable to a wide Kn range are proposed for micro shear flows. Furthermore, 3-D micro flows in a slider air bearing and micro flows in a??slip flowa?? and a??transition flowa?? regime in micro ducts with different cross-sections are studied using present DSMC method.