A Non-Negative Least Squares-based Approach for Moment-Preserving Particle Merging

In the present work, a novel particle merging scheme is proposed for PIC-DSMC simulations, based on the solution of a Non-negative Least Squares problem. The merging algorithm conserves arbitrary moments of the velocity distribution function, and a collision rate-conserving version of the algorithm is presented as well. Numerical simulations show excellent performance of the merging algorithm in terms of accuracy.