Low Pressure Gas Modeling

We are experts in developing gas flow models that leverage the direct simulation Monte Carlo (DSMC) method in understanding low-pressure, or rarefied, gas flows.

These flows occur when the mean free path, or average distance between molecular collisions, exceeds the characteristic length scales of the gas.  This can occur through low pressure and/or small length scales, which is experienced within the space environment, upper atmosphere, and in vacuum chamber conditions.  The DSMC method can capture unsteady, rarefied flows with complex geometric representations.  For example, the video shows gas molecules from a DSMC simulation through a bell vacuum chamber.

DSMC prediction of gas molecules moving through a vacuum chamber. The chamber walls have a sticking coefficient of 1.

technical Contact

Dr. Tim Deschenes


  • Prediction of rarefied micro-nozzle flows using the SPARTA library

    The accurate numerical prediction of gas flows within micro-nozzles can help evaluate the performance and enable the design of optimal configurations for micro-propulsion systems. Viscous effects within the large boundary layers can have a strong impact on the nozzle performance. Furthermore, the variation in collision length scales from continuum to rarefied preclude the use of continuum-based computational fluid dynamics.

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  • Development of the ARISTOTLE webware

    Rarefied gas dynamics are important for a wide variety of applications. An improvement in the ability of general users to predict these gas flows will enable optimization of current, and discovery of future processes. Despite this potential, most rarefied simulation software is designed by and for experts in the community. This has resulted in low adoption of the methods outside of the immediate RGD community. This paper outlines an ongoing effort to create a rarefied gas dynamics simulation tool that can be used by a general audience.

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  • Simulation framework for space environment ground test fidelity

    We present initial work to develop an extensible model for spacecraft environmental interactions. The starting point for model development is a rarefied gas dynamics model for hyperthermal atomic oxygen. The space envi- ronment produces a number of challenging stimuli, including atomic oxygen, but also charged particles, magnetic fields, spacecraft charging, ultraviolet radiation, micrometeoroids, and cryogenic temperatures.

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Spectral Science, Inc