SPARTA Features

SPARTA is a Direct Simulation Monte Carlo (DSMC) code, suitable for modeling low-density gases. It has these general classes of functionality:

• General features
• Models
• Geometry
• Gas-phase collisions and chemistry
• Surface collisions
• Performance
• Diagnostics
• Output
• Pre- and post-processing

A general overview of SPARTA is given in the intro section of the SPARTA documentation. To learn details of a feature, find the input script command(s) that implement it, and read their doc pages.

General features

• runs on a single processor or in parallel
• distributed-memory message-passing parallelism (MPI)
• spatial-decomposition of simulation domain for parallelism
• open-source distribution
• highly portable C++
• optional libraries used: MPI
• easy to extend with new features and functionality
• runs from an input script
• syntax for defining and using variables and formulas
• syntax for looping over runs and breaking out of loops
• run one or multiple simulations simultaneously (in parallel) from one script
• build as library, invoke SPARTA thru library interface or provided Python wrapper
• couple with other codes: SPARTA calls other code, other code calls SPARTA, umbrella code calls both

Models

• 3d or 2d or 2d-axisymmetric domains
• variety of global boundary conditions
• create particles within flow volume or at inlet boundaries
• emit particles from simulation box faces due to flow properties
• emit particles from simulation box faces due to profile defined in file
• emit particles from surface elements due to normal and flow properties
• ambipolar approximation for ionized plasmas

Geometry

• Cartesian, heirarchical grids with multiple levels of local refinement
• create grid from input script or >read from file
• embed :triangulated (3d) or line-segmented (2d) surfaces in grid, read in from file

Gas-phase collisions and chemistry

• collisions between all particles or pairs of species groups within grid cells
• collision models: VSS (variable soft sphere), VHS (variable hard sphere), HS (hard sphere)
• chemistry models: TCE, QK

Surface collisions and chemistry

• for surface elements or global simulation box boundaries
• collisions: specular or diffuse
• reactions

Performance

• grid cell weighting of particles
• adaptation of the grid cells between runs
• on-the-fly adaptation of the grid cells
• static load-balancing of grid cells or particles
• dynamic load-balancing of grid cells or particles

Diagnostics

• global boundary statistics
• per grid cell statistics
• per surface element statistics
• time-averaging of global, grid, surface statistics

Output

• log file of statistical info
• dump files (text or binary) of per particle, per grid cell, per surface element values
• binary restart files
• on-the-fly rendered images and movies of particles, grid cells, surface elements

Pre- and post-processing

• Various pre- and post-processing serial tools are packaged with SPARTA; see Section 7 of the manual.
• Our group has also written and released a separate toolkit called Pizza.py which provides tools for doing setup, analysis, plotting, and visualization for SPARTA simulations. Pizza.py is written in Python and is available for download from the Pizza.py WWW site.