Dresden 2009 – wissenschaftliches Programm
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VA: Fachverband Vakuumphysik und Vakuumtechnik
VA 4: Diffusion, magnetic thin films
VA 4.1: Vortrag
Montag, 23. März 2009, 15:30–15:50, HSZ 101
Simulation of Diffusion Processes in Rarefied Gases - A Hybrid Approach — David Sinz1,2, •Jens Harting1, Franz Keller2, and Ulrich Nieken2 — 1Institut für Computerphysik, Pfaffenwaldring 27, 70569 Stuttgart — 2Institut für Chemische Verfahrenstechnik, Böblinger Str. 72, 70199 Stuttgart
We simulate diffusion-convection problems in rarefied gases in order to predict the diffusive spreading of low concentrated contaminants in a stream of purge gas.
The proposed simulation method is a hybrid approach combining the lattice Boltzmann method (LBM) and a simplified molecular dynamics (MD) approach. Here, the flow field of the purge gas is simulated using the LBM and the behaviour of the contaminants is described by a MD approach neglecting the interaction of the particles with each other and the gas. The influence of the purge gas on the contaminants is modeled by central collisions with pseudo particles, where the collision frequency dependents on the mean free path of the MD particles. The velocity of the pseudo particles is determined by the predicted flow field of the purge gas as well as thermal fluctuations.
Our approach requires substantially less computing time than a regular MD approach and allows the simulation of systems of technically interesting dimensions. The method is evaluated by comparing simulation results to analytical solutions for simple test cases as well as to experimental data for a more complex case both with acceptable agreement.