  The present work introduces a simple, yet effective particle coalescing
procedure for two-dimensional SPH simulations with spatially varying
resolution. In addition to the regular conservation properties of former
algorithms concerning the mass and linear momentum, the current model provides
the exact conservation of the angular momentum as well. The detailed discussion
of the coalescing method is followed by its verification through a frozen
Taylor-Green vortex example with gradually derefined particle configuration. As
a demonstration of the applicability of the proposed technique, a typical
weakly compressible dam break simulation and an evolution of a two-dimensional
Taylor-Green vortex pattern with local refinement are presented and comparisons
are made with analytical and experimental data.
