Scaling and Visualization of N-Body Gravitational Dynamics with GalaxSeeHPC

Volume 5, Issue 1 (August 2014), pp. 10–22

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@article{jocse-5-1-2,
  author={David A. Joiner and James Walters},
  title={Scaling and Visualization of N-Body Gravitational Dynamics with GalaxSeeHPC},
  journal={The Journal of Computational Science Education},
  year=2014,
  month=aug,
  volume=5,
  issue=1,
  pages={10--22},
  doi={https://doi.org/10.22369/issn.2153-4136/5/1/2}
}

In this paper, we present GalaxSeeHPC, a new cluster-enabled gravitational N-Body program designed for educational use, along with two potential student experiences that illustrate what students might be able to investigate at larger N than available with earlier versions of GalaxSee. GalaxSeeHPC adds additional force calculation algorithms and input options to the previous clusterenabled version. GalaxSeeHPC lessons have been developed focusing on two key studies, the structure of rotating galaxies and the large scale structure of the universe. At large N, visualizing the results becomes a significant challenge, and tools for visualization are presented. The canonical lesson in the original version of GalaxSee is the rotation and flattening of a cluster with angular momentum. Model discrepancies that are not obvious at the range of N available in previous versions become quite obvious at large N, and changes to the initial mass and velocity distribution can be seen more readily. For the large scale structure models, while basic clearing and clustering can be seen at around N=5,000, N=50,000 allows for a much clearer visualization of the filamentary structure at large scale, and N=500,000 allows for a more detailed geometry of the knots formed as the filaments combine to form superclusters. For the galactic dynamics simulations, we found that while a flattening due to overall angular momentum can be explored with N=1,000 or smaller, formation of spiral structure requires not only a larger number of objects, typically on the order of 10,000, but also modifications to the default initial mass and velocity distributions used in older versions of GalaxSee.