Buchumschlag

Modeling the Flow of Rarefied Gases at NASA

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Veröffentlicht in:NASA Center for AeroSpace Information (CASI). Conference Proceedings (Sep 21, 2012)
1. Verfasser: Lumpkin, Forrest E, III
Veröffentlicht:
NASA/Langley Research Center
Schlagworte:
Time dependence
Performance enhancement
Diatomic molecules
Graphics processing units
Quantum mechanics
Relaxation time
Classical mechanics
Atmospheric models
Mechanical properties
Thermal energy
Molecular collisions
Collision dynamics
Diatomic gases
Computer simulation
Rarefied gases
Computer architecture
Monte Carlo simulation
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Abstract:At modest temperatures, the thermal energy of atmospheric diatomic gases such as nitrogen is primarily distributed between only translational and rotational energy modes. Furthermore, these energy modes are fully excited such that the specific heat at constant volume is well approximated by the simple expression C(sub v) = 5/2 R. As a result, classical mechanics provides a suitable approximation at such temperatures of the true quantum mechanical behavior of the inter-molecular collisions of such molecules. Using classical mechanics, the transfer of energy between rotational and translation energy modes is studied. The approach of Lordi and Mates is adopted to compute the trajectories and time dependent rotational orientations and energies during the collision of two non-polar diatomic molecules. A Monte-Carlo analysis is performed collecting data from the results of many such simulations in order to estimate the rotational relaxation time. A Graphical Processing Unit (GPU) is employed to improve the performance of the Monte-Carlo analysis. A comparison of the performance of the GPU implementation to an implementation on traditional computer architecture is made. Effects of the assumed inter-molecular potential on the relaxation time are studied. The seminar will also present highlights of computational analyses performed at NASA Johnson Space Center of heat transfer in rarefied gases.
Quelle:Advanced Technologies & Aerospace Database