Generalized and high-efficiency arbitrary-positioned buffer for smoothed particle hydrodynamics

This paper develops a generalized, high-efficiency buffer for particle generation and deletion at arbitrary-positioned in-/outlets in the smoothed particle hydrodynamics method. To achieve generality, we standardize the position comparison of particles with an arbitrary-positioned in-/outlet bound by introducing coordinate transformation. To enhance efficiency, particle candidates subjected to position comparison at a specific in-/outlet are restricted to those within the local cell-linked lists near the defined buffer region, thereby avoiding the inefficiency in the straightforward approach of sequentially checking all fluid particle positions across the computational domain. We validate the effectiveness and versatility of the developed buffer through two-dimensional and three-dimensional non-orthogonal and orthogonal, uni- and bidirectional flows with arbitrary-positioned in- and outlets, driven by pressure or velocity boundary conditions.