Data Management and Volcano Plume Simulation with Parallel SPH Method and Dynamic Halo Domains

This paper presents data management and strategies for implementing smoothed particle hydrodynamics (SPH) method to simulate volcano plumes. These simulations require a careful definition of the domain of interest and multi-phase material involved in the flow, both of which change over time and involve transport over vast distances in a short time. Computational strategies are developed to overcome these challenges by building mechanisms for efficient creation and deletion of particles for simulation, parallel processing (using the message passing interface (MPI)) and a dynamically defined halo domain (a domain that ”optimally” captures all the material involved in the flow). A background grid is adopted to reduce neighbor search costs and to decompose the domain. A Space Filing Curve (SFC) based ordering is used to assign unique identifiers to background grid entities and particles. Time-dependent SFC based indices are assigned to particles to guarantee uniqueness of the identifier. Both particles and background grids are managed by hash tables which can ensure quick and flexible access. An SFC based three dimensional (3D) domain decomposition and a dynamic load balancing strategy are implemented to ensure good load balance. Several strategies are developed to improve performance: dynamic halo domains, calibrated particle weight and optimized work load check intervals. Numerical tests show that our code has good scalability and performance. The strategies described in this paper can be further applied to many other implementations of mesh-free methods, especially those implementations that require flexibility in adding and deleting of particles.