The DS2G program is a general program for the computation
of two-dimensional or axially symmetric flows by the direct simulation
Monte Carlo (DSMC) method. The sampling of the flows may be either
for a permanently unsteady flow (with or without ensemble averaging)
or for a time averaged steady flow at large times. It is a self-contained
executable program for Intel based (486DX or higher) PC's. The
data input is through a series of on-screen menus. The output
can be through text files and/or files for the TECPLOT post-processing
A self-extracting ZIP file to produce the file DS2G.EXE can
be downloaded (470kb) as
The data files for the demonstration cases may be downloaded
(20 kb) as the self-extracting ZIP file
The user manual for Version 3.2 can be downloaded (748 kb)
- Version 1.0 of this program was released in February 1995.
Its capabilities were generally similar to the earlier G2 programs,
although it allowed in-plane moving surfaces in two-dimensional
flows and spinning surfaces in axially symmetric flows.
- Version 1.1 allowed surfaces to be catalytic for recombination
reactions, the circmferential surface velocity could be specified
as an angular velocity, and molecules that were lost through
round-off error were balanced by the duplication of a nearby
- Version 2 introduced a new and faster logic for the molecule
moves, together with consequential changes.
- Version 2.1 (January 1996) allowed different initial conditions
in each flow region. This increased the range of unsteady flow
problems that can be simulated by the program. In addition, the
flux of molecules between regions was sampled.
- Version 2.2 (May 1996) includes a three-dimensional plot
option for the TECPLOT output for steady axially symmetric flows.
The text output file has been split into separate files.
- Version 2.3 (December 1996) allows displacement of interfaces
for the setting of periodic boundaries, introduces power-law
options for the setting of surface and specified input boundary
properties, and allows the molecules from one case to be used
as the initial state of a new case.
- Version 3.0 (March 1998) replaces fixed sub-cells by adaptive
transient sub-cells that are defined one cell at a time and are
called only from the collision subroutine. For the first demonstration
case, the mean spacing between collision pairs is reduced by
60%, the execution time is reduced by 15%, and the storage required
by the cell structure has been more than halved. This is particularly
useful for unsteady flow calculations without ensemble averaging
and the program has been modified to facilitate these calculations.
The downloadable program is now restricted to 200,000 simulated
molecules, but an unrestricted version is available to registered
users (application via e-mail).
- Version 3.1 (August 1998) adds diagnostic output to the TECPLOT
file that indicates whether the DSMC criteria have been met.
The number of molecules in not restricted, but I would like to
hear from new users.
- Version 3.2 (June 1999) adds an adiabatic diffuse (zero heat
transfer) option to the surface properties. This is activated
by setting a surface temperature to -2. (specular reflection
now requires -1.). The surface recovery temperature is output
in a new column in DS2GS.TXT.
In addition, program bugs have been progressively
corrected.The current file is dated 13 June, 1999
purpose of the programs is to demonstrate the DSMC method. They
are nor guaranteed to be free of error and should not be relied
upon for solving problems where an error could result in injury
or loss. If the programs are used for such solutions, it is entirely
at the user's risk.
Further enquiries should be addressed to Graeme Bird