EPIC: The Elliptical Parcel-In-Cell method

We introduce a novel Elliptical Parcel-In-Cell (EPIC) method for the simulation of fluid flows. The Lagrangian parcels are represented by ellipsoids which deform, rotate and move in the flow field. The splitting of excessively elongated parcels and the merging of very small parcels with their nearest other parcel gives rise to a natural mixing mechanism. The parcel merging algorithm involves analysing a graph of nearest neighbouring parcels, which can be on different MPI processes. The communication in this algorithm was implemented using one-sided (RMA) communication. The EPIC method has proven to outperform non-deformable PIC methods and comparable Eulerian models for buoyancy-driven turbulent fluid flows in terms of effective small-scale resolution.