Control of the number of particles in fluid and MHD particle in cell methods Original Research Article

We describe an algorithm to control the number of particles in fluid, particle-in-cell calculations. In problems with large variations in mass density or grid spacing, the ability to increase or decrease the number of particles in each cell of the mesh becomes essential. Here, a cell-by-cell replacement algorithm which preserves grid data and positivity of the particle data, where appropriate, is described. The algorithm preserves contact discontinuities, introduces little diffusion, and adds little or nothing to the cost of a calculation.