Sponsored by BMBF Logo


Background and purpose

Nbody6++ is a member of a family of high accuracy direct
N-body integrators used for simulations of dense star clusters,
galactic nuclei, and problems of star formation. It is a special
version of Nbody6 optimised for massively parallel computers.

Some of the most important applications are simulations of rich open and
globular clusters with a large number of binaries and galactic nuclei
with single and binary black holes. The dynamic range required for
the simulation ranges from 108 years (relaxation time) over
106 years (typical orbital time of one star in the cluster) to
several days (periods of most compact binaries). These data demand
a high-order integration scheme, with regularisations, and an
Ahmad-Cohen neighbour scheme. Only ten years ago the maximum number
of particles we could simulate with the supercomputers was 104,
and only due to the use of special purpose GRAPE accelerator boards
we can now with our recent parallel GRAPE clusters tackle the
one million body limit. Some more citations on the code and its scientific use
can be found in the relevant sections of the soon to be published App2Grid-Guide.

AstroGrid-D deployment

A deployment package has been developed within AstroGrid-D to submit,
monitor and kill Nbody6++ jobs using AstroGrid-D and D-Grid resources.
Apart from the deployment this package provides automatic data staging,
that is, the Nbody6++ input and output files are automatically transferred
back and forth. A brief instruction is available for download (PDF) . There is
also an online documentation under  AGDGUIDE local web resource at ZAH (T. Brüsemeister).


Xnbody the online visualisation tool for Nbody6++ enables scientists
to visualise the internal dynamical evolution of stellar systems like
globular clusters on time scales of the order of the relaxation time.
In particular, one can trace orbits of individual stars using a buffering
mechanism and employ different color schemes i.e. coloring by mass,
velocity, force, jerk and other attributes. In addition, Xnbody is able to
visualise the orbital evolution of star clusters which are subject to
dynamical friction in corresponding galaxy models and tidal effects as well.
Xnbody is based on the class libraries Qt and VTK and makes use of the
coupling library VISIT, which has been developed at the Research Center Juelich.


AstroGrid-D Tutorial (PDF)


Nbody6++: R. Spurzem (ARI/ZAH)
AstroGrid-D deployment package: T. Brüsemeister (ARI/ZAH)