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Axisymmetric Implementation for 3D-Based DSMC CodesThe primary objective in developing NASA s DSMC Analysis Code (DAC) was to provide a high fidelity modeling tool for 3D rarefied flows such as vacuum plume impingement and hypersonic re-entry flows [1]. The initial implementation has been expanded over time to offer other capabilities including a novel axisymmetric implementation. Because of the inherently 3D nature of DAC, this axisymmetric implementation uses a 3D Cartesian domain and 3D surfaces. Molecules are moved in all three dimensions but their movements are limited by physical walls to a small wedge centered on the plane of symmetry (Figure 1). Unfortunately, far from the axis of symmetry, the cell size in the direction perpendicular to the plane of symmetry (the Z-direction) may become large compared to the flow mean free path. This frequently results in inaccuracies in these regions of the domain. A new axisymmetric implementation is presented which aims to solve this issue by using Bird s approach for the molecular movement while preserving the 3D nature of the DAC software [2]. First, the computational domain is similar to that previously used such that a wedge must still be used to define the inflow surface and solid walls within the domain. As before molecules are created inside the inflow wedge triangles but they are now rotated back to the symmetry plane. During the move step, molecules are moved in 3D but instead of interacting with the wedge walls, the molecules are rotated back to the plane of symmetry at the end of the move step. This new implementation was tested for multiple flows over axisymmetric shapes, including a sphere, a cone, a double cone and a hollow cylinder. Comparisons to previous DSMC solutions and experiments, when available, are made.
Document ID
20110015744
Acquisition Source
Johnson Space Center
Document Type
Conference Paper
Authors
Stewart, Benedicte (NASA Johnson Space Center Houston, TX, United States)
Lumpkin, F. E. (NASA Johnson Space Center Houston, TX, United States)
LeBeau, G. J. (NASA Johnson Space Center Houston, TX, United States)
Date Acquired
August 25, 2013
Publication Date
September 25, 2011
Subject Category
Fluid Mechanics And Thermodynamics
Report/Patent Number
JSC-CN-24653
Meeting Information
Meeting: Direct Simulation Monte Carlo 2011
Location: Santa Fe, NM
Country: United States
Start Date: September 25, 2011
End Date: September 28, 2011
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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