Parallel simulation of microflows by DSMC and Burnett equations.

摘要

The primary objective of this dissertation is to numerically simulate and study the heat transfer and flow characteristics in fluidic microelectromechanical system (MEMS). In typical microfluidic MEMS applications, the ratio of the gas mean-free-path to the characteristic length scale, or the Knudsen number, can be large. The traditional mathematical models of continuum fluid based on the Navier-Stokes equations may become invalid because of their constitutive relations of viscous stress and heat flux.; In this study, the direct simulation Monte Carlo (DSMC) method and the conventional Burnett equations are applied to model the microflows in microchannels from molecular and continuum point of view, respectively. The DSMC method has been implemented for a distributed parallel-computing environment with an excellent parallel efficiency. The Knudsen number effects on the viscous stress and heat transport are simulated and analyzed. The results of the microfluidic flow simulations show significantly different flow characteristics and heat transfer behavior compared with macroscale phenomena.; In addition, a parallel unsteady DSMC algorithm is also developed to study the time-dependent behavior of an initially chaotic micro-Couette flow. The results of the simulations show that the particle-based DSMC method has the capability to capture the nonlinear evolution of harmonic waves.