Electromagnetic particle-in-cell (EMPIC) codes provide a capability for numerically simulating the motions of electrically charged particles in electromagnetic fields, and hence have become standard software tools in plasma physics research. Most existing EMPIC codes are based on the use of orthogonal computational grids (Cartesian or cylindrical). The applicability of such codes is restricted to problems with simple geometries.

A new, three-dimensional (3D) EMPIC algorithm using nonorthogonal grids has been developed recently for parallel supercomputers. The algorithm and a computer code that implements this algorithm can be used to study plasma problems involving complex geometries, such as those related to microwave devices.

One prior EMPIC algorithm using nonorthogonal grids is based on a finite-element approach. The present algorithm and code are based on a finite-volume approach. The major features of the present algorithm are the following:

  • The building blocks of computational grids are logically connected, nonorthogonal, deformable hexahedral cells. As a result, grids can be made to accommodate complex geometries for large-scale simulations of plasmas.
  • The electromagnetic-field-update phase of the computational cycle is based on a discrete-volume generalization of the standard finite-difference time-domain (FDTD) algorithm; this formulation makes the algorithm simpler than the corresponding finite-element-based algorithm.
  • The particle-push phase of the computational cycle involves a hybrid logical/physical-space operation.
  • The implementation of this algorithm uses a domain decomposition of a grid and particles that is almost identical to that of a Cartesian grid based EMPIC algorithm.

The combination of features makes it possible to perform 3D large-scale simulations of plasma physics problems involving complex geometries with a very high parallel-computing efficiency (> 96 percent).

This work was done by Joseph Wang, Paulett Liewer, Dimitri Kondrashov, and Steve Karmesin of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp  under the Physical Sciences category. NPO-20496


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Parallel 3D EMPIC algorithm using nonorthognal grids

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This article first appeared in the February, 2000 issue of NASA Tech Briefs Magazine.

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