Nearest-Grid-Point Interpolation in Gyrokinetic Particle-in-Cell Simulation

✍ Scribed by Scott E. Parker

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 319 KB
• Volume: 178
• Category: Article
• ISSN: 0021-9991
• DOI: 10.1006/jcph.2002.7039

✦ Synopsis

Linear interpolation or other higher order interpolation schemes are almost always used in particle-in-cell simulation because of their lower noise characteristics and accuracy relative to the nearest-grid-point method. The higher order interpolation schemes are chosen because of their optimal performance, balancing a smaller number of particles against more computer operations per particle per time step. However, this is not the case in large-scale gyrokinetic particle simulations, where sometimes nearest-grid-point interpolation is used with results virtually identical to those of linear interpolation using the same number of particles. Here, a comparison and analysis of nearest-grid-point and linear interpolation schemes is given showing why nearest-grid-point interpolation can be optimal. A simple two-dimensional slab model of the ion-temperature-gradient instability and associated generation of zonal flows is used to compare the interpolation schemes. Significant improvements in performance are possible by using nearest-grid-point interpolation because of the large number of gathers/scatters associated with gyroaveraging.