Direct simulation Monte Carlo
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Direct Simulation Monte Carlo (DSMC) method uses probabilistic (Monte Carlo) simulation to solve the Boltzmann equation for finite Knudsen number fluid flows.
The DSMC method was proposed by Prof. Graeme Bird[1][2][3], Emeritus Professor of Aeronautics, University of Sydney. DSMC is a numerical method for modeling rarefied gas flows, in which the mean free path of a molecule is of the same order (or greater) than a representative physical length scale (i.e. the Knudsen number Kn is greater than 1). In supersonic and hypersonic flows rarefaction is characterized by Tsein's parameter, which is equivalent to the product of Knudsen number and Mach number (KnM) or M2/Re, where Re is the Reynolds number. [4][5] In these rarefied flows, the Navier-Stokes equations can be inaccurate. The DSMC method has been extended to model near continuum flows (Kn < 1).
The DSMC method models fluid flows using simulation molecules which represent a large number of real molecules in a probabilistic simulation to solve the Boltzmann equation. Molecules are moved through a simulation of physical space in a realistic manner that is directly coupled to physical time such that unsteady flow characteristics can be modeled. Intermolecular collisions and molecule-surface collisions are calculated using probabilistic, phenomenological models. Common collision models include the Hard Sphere model, the Variable Hard Sphere (VHS) model, and the Variable Soft Sphere (VSS) model. The fundamental assumption of the DSMC method is that the molecular movement and collision phases can be decoupled over time periods that are smaller than the mean collision time.
Currently the DSMC method has been applied to the solution of flows ranging from estimation of the Space Shuttle re-entry aerodynamics, to the modeling micro-electro-mechanical systems (MEMS).
[edit] References
- ^ G. A. Bird, 'Approach to translational equilbrium in a rigid sphere gas', Phys. Fluids, 6, p1518 (1963).
- ^ G. A. Bird, Molecular Gas Dynamics, Clarendon, Oxford (1976)
- ^ G. A. Bird, Molecular Gas Dynamics and the Direct Simulation of Gas Flows, Claredon, Oxford (1994)
- ^ H. S. Tsein, 1948 ‘Superaerodynamics, mechanics of rarefied gases’ J. Aerospace Sci, 13, p342, 1946.
- ^ M. N. Macrossan, 'Scaling Parameters for Hypersonic Flow: Correlation of Sphere Drag Data'. In: M. S. Ivanov and A. K. Rebrov, 25th International Symposium on Rarefied Gas Dynamics, Siberian Branch of the Russian Academy of Sciences, p.759 (2007).
[edit] External links
- Comments on DSMC by Graeme Bird
- DSMC Demo Applet
- Introduction to writing DSMC codes
- Course material on DSMC (part of Computational Physics tutorial by Franz J. Vesely, University of Vienna)
