Monte Carlo Modeling of Micro-Scale Gas Flows


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In the past few years, an information preservation (IP) method [1-6] has emerged as a numerical technique to analyze subsonic, micro-scale gas flows. In this method, simulated molecules move through physical space and undergo collisions appropriate to the thermal velocities using the same algorithms and models as the direct simulation Monte Carlo (DSMC) method [7], while the macroscopic observable quantities, such as velocity and surface shear stress, are obtained through averaging appropriate physical information carried along with the simulated molecules. The physical information, updated by additional treatments [3-6], reflects the collective behavior of the enormous number of real molecules represented by each simulated molecule in the DSMC method, and therefore it is not subject to the statistical noise caused by the thermal velocity. This method was successfully applied to benchmark problems, namely Couette flow, Poiseuille flow and Rayleigh flow [1,2]. The IP results were in excellent agreement with the exact solutions in the continuum and free molecular regimes, and with the linearized Boltzmann solutions [8,9] and experimental data [10] in the transition regime. Sun et al [5] simulated low subsonic airflows past a micro flat plate using the IP method, and the calculated drag coefficient compared well with experimental data of Schaff & Sherman [11], and Janour [12]. Sun & Boyd [6] introduced an additional energy transfer model to update the information temperature that successfully solved the thermal Couette flow over the entire flow regime. This paper will report some recent work about micro-scale gas flows in our group. Stream-wise pressure distributions and mass fluxes through micro-channels given by the IP method agree well with experimental data measured by Pong et al [13], Shih et al [14], and Arkilic et al [15], respectively. The famous Knudsen minimum of normalized mass flux is observed in IP and DSMC calculations of a short micro-channel over the entire flow regime, whereas the slip Navier-Stokes solution fails to predict it. In IP calculating micro square-cavity flows, the boundary conditions in the regions near the angle points with singularity are investigated. The IP results in the continuum regime compare well with the Navier-Stokes solution of Ghia et al [16] and the BGK solution of Su et al [17].

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Journal: TechConnect Briefs
Volume: 2, Technical Proceedings of the 2003 Nanotechnology Conference and Trade Show, Volume 2
Published: February 23, 2003
Pages: 448 - 451
Industry sectors: Advanced Materials & Manufacturing | Sensors, MEMS, Electronics
Topic: MEMS & NEMS Devices, Modeling & Applications
ISBN: 0-9728422-1-7