The overlapping particle technique for multi-resolution simulation of particle methods

A multi-resolution technique for particle methods, the overlapping particle technique (OPT), is explained in detail. The OPT expresses a whole simulation domain with partially overlapping sub-domains with their own spatial resolutions and particle shape. For, example, the OPT allows us to connect a sub-domain of fine spherical particles with a sub-domain of coarse ellipsoidal particles. Sub-domains are bilaterally coupled by mapping and inlet-outlet boundaries. Techniques for reducing error of the total fluid mass were also newly added to the OPT. The OPT was applied to the moving particle semi-implicit (MPS) method, the explicit moving particle simulation (EMPS) method, and smoothed particle hydrodynamics (SPH). Verification and validation analyses of the OPT were carried out. As a result, the OPT was shown to reduce the required number of particles and the computational time of particle simulations while maintaining the robustness of particle simulations. It was also shown that the error of the total fluid mass was sufficiently small for most engineering problems.