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Abstract In this paper, we develop an optimal particle setup method for initial condition with Centroidal Voronoi Particle (CVP) dynamics, which combines the Centroidal Voronoi Tessellation (CVT) and Voronoi Particle (VP) concept. CVT optimizes the energy function in terms of compactness and consequently ensures the isotropy of particle distribution. The CVT configuration is computed by Lloyd's algorithm, which decreases the energy function monotonically. A physics-motivated model equation with tailored equation of state (EOS) is employed to relax the Voronoi particle system such that the convergent equilibrium matches the target configuration. The resulting particle distribution approximates the given analytical profiles of spatially adaptive density, smoothing-length and mass distribution with high interpolation accuracy. The level-set method is introduced to describe arbitrarily complex geometries. A set of Smoothed Particle Hydrodynamics (SPH) simulations is computed to demonstrate the performances of the proposed method. Without parameter tuning, good performance is obtained for presented benchmarks implying its promising potential. [ABSTRACT FROM AUTHOR]

Abstract: We describe the algorithms implemented in the first version of GRADSPH, a parallel, tree-based, smoothed particle hydrodynamics code for simulating self-gravitating astrophysical systems written in FORTRAN 90. The paper presents details on the implementation of the Smoothed Particle Hydro (SPH) description, where a gridless approach is used to model compressible gas dynamics. This is done in the conventional SPH way by means of ‘particles’ which sample fluid properties, exploiting interpolating kernels. The equations of self-gravitating hydrodynamics in the SPH framework are derived self-consistently from a Lagrangian and account for variable smoothing lengths (‘GRAD-h’) terms in both the hydrodynamic and gravitational acceleration equations. A Barnes–Hut tree is used for treating self-gravity and updating the neighbour list of the particles. In addition, the code updates particle properties on their own individual timesteps and uses a basic parallelisation strategy to speed up calculations on a parallel computer system with distributed memory architecture. Extensive tests of the code in one and three dimensions are presented. Finally, we describe the program organisation of the publicly available 3D version of the code, as well as details concerning the structure of the input and output files and the execution of the program. Program summary: Program title: GRADSPH 1.0 Catalogue identifier: AECX_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AECX_v1_0.html Program obtainable from: CPC Program Library, Queen''s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 11 123 No. of bytes in distributed program, including test data, etc.: 1 561 909 Distribution format: tar.gz Programming language: Fortran 90/MPI Computer: HPC cluster Operating system: Unix Has the code been vectorised or parallelised?: Yes RAM: 56 Mwords with 1.2 million particles on 1 CPU Word size: 32 bits Classification: 12 Nature of problem: Evolution of a self-gravitating fluid. Solution method: Hydrodynamics is described using SPH, self-gravity using the Barnes–Hut tree method. Running time: The test case provided with the distribution takes less than 10 minutes for 500 time steps on 10 processors. [Copyright &y& Elsevier]

Abstract: This paper presents a new contact algorithm to analyze an elasto-plastic contact problem using the SPH (Smoothed Particle Hydrodynamics) method. This algorithm is available to both contact types, which are the particle-to-particle contact and the surface-to-particle one. It is employed to determine the actual boundary normal vector and apply the reproducing condition in the cylindrical coordinate. The variational equation based on the virtual work principle is derived and its solution is obtained by the penalty method, which includes both a penetration and a penetration rate. Numerical simulations are presented to show that the proposed algorithm can be applied to the elasto-plastic contact problem for the case that either both bodies are deformable or one is a rigid wall and the other is deformable. Two colliding bodies can be separated with the expected rebound velocity and the total contact force acting on between them similar to theoretical value. Results of the rod impact analysis are shown to be in agreement with the ones obtained by other solution and experiment. [Copyright &y& Elsevier]