Gridless DSMC

Olson, Spencer E.; Christlieb, Andrew

doi:10.1016/j.jcp.2008.04.038

Cited by 28 publications

(13 citation statements)

References 42 publications

(64 reference statements)

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“…A common feature in most DSMC collision procedures involves the sorting of macro-particles into "collision cells" [9,48], the exception being gridless DSMC methods [43,44]. In collision cell approaches, candidate collision pairs are selected from a computational cell based on collision rates described by kinetic theory [7].…”

Section: The Direct Simulation Monte Carlo Methodsmentioning

confidence: 99%

pdFOAM: A PIC-DSMC code for near-Earth plasma-body interactions

et al. 2017

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Understanding the interaction of the near-Earth space environment with orbiting bodies is critical, both from a design and scientific perspective. In Low Earth Orbit (LEO), the interaction between the ionosphere and orbiting objects is well studied from a charging perspective. Not well understood is the effect of the ionosphere on the motion of LEO objects i.e. charged aerodynamics. This paper presents the implementation, validation, and verification of the hybrid electrostatic Particle-in-Cell (PIC) -Direct Simulation Monte Carlo (DSMC) code, pdFOAM, to study both the neutral and charged particle aerodynamics of LEO objects. The 2D aerodynamic interaction of a cylinder with a fixed uniform surface potential of −50 V and mesothermal O + and H + plasmas representative of ionospheric conditions is investigated. New insights into the role of bounded ion jets and their effect on surface forces are presented. O + bounded ion jets are observed to cause a 4.4% increase ion direct Charged Particle Drag (dCPD), while H + ion jets produce a net reduction in H + drag by 23.7% i.e. they cause a thrust force. As a result, we conclude that past work, primarily based on Orbital Motion Limited theory, does not adequately capture the physics of LEO charged aerodynamics. Hence, we recommend a revisit of conclusions regarding the significance of CPD to LEO objects -pdFOAM being an appropriate tool for this purpose.

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Section: The Direct Simulation Monte Carlo Methodsmentioning

confidence: 99%

pdFOAM: A PIC-DSMC code for near-Earth plasma-body interactions

et al. 2017

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“…It seems therefore likely that the discontinuous, cell based delocalisation of the coagulation interaction used for numerical purposes in [15] is not well suited to more than one spatial dimension and that smoother delocalisations should be used. Similar methods have been used for the simulation of Boltzmann gases [13].…”

Section: Discussionmentioning

confidence: 99%

Properties of the solutions of delocalised coagulation and inception problems with outflow boundaries

Patterson

2015

J. Evol. Equ.

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Well posedness is established for a family of equations modelling particle populations undergoing delocalised coagulation, advection, inflow and outflow in a externally specified velocity field. Very general particle types are allowed while the spatial domain is a bounded region of d-dimensional space for which every point lies on exactly one streamline associated with the velocity field. The problem is formulated as a semi-linear ODE in the Banach space of bounded measures on particle position and type space. A local Lipschitz property is established in total variation norm for the propagators (generalised semi-groups) associated with the problem and used to construct a Picard iteration that establishes local existence and global uniqueness for any initial condition. The unique weak solution is shown further to be a differentiable or at least bounded variation strong solution under smoothness assumptions on the parameters of the coagulation interaction. In the case of one spatial dimension strong differentiability is established even for coagulation parameters with a particular bounded variation structure in space. This one dimensional extension establishes the convergence of the simulation processes studied in [Patterson, Stoch. Anal. Appl. 31, 2013] to a unique and differentiable limit.

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“…To ensure this, in the octree construction, recursive division is stopped when the number of particles in the node is less than a value, ζ, which represents the maximum number of particles per node. 16 The exact value of ζ, such that the resulting leaf nodes have dimensions less than the local mean free path, is determined based on trial and error. Figures 2 and 3 show a one-and two-dimensional tree structure, respectively, and the value of ζ is set to three in the quadtree example.…”

Section: A Morton Z-curve Enabled Octree Structurementioning

confidence: 99%

A Hybrid CPU-GPU Parallel Octree Direct Simulation Monte Carlo Approach

Jambunathan

Levin

2015

22nd AIAA Computational Fluid Dynamics Conference

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The gridfree octree DSMC approach is parallelized with GPGPUs using CUDA. A linear space filling Morton Z-curve is employed to represent the three dimensional octree structure in a linear array and the advantages of this implementation is discussed. The methodology for a multi-GPU, hybrid MPI-CUDA implementation, involving load balanced domain decomposition and inter-GPU communications is presented. Nearly 70-90 times speedup was achieved by the multi-GPU CHAOS solver using 8 GPUs as compared to the serial octree DSMC implementation. When compared to a single GPU, the simulation performed using 8 GPUs showed 5-6 times speedup, i.e., an efficiency of 55-75% was achieved depending on the type of flow condition being analysed. The single-GPU simulations exhibited 12-30 times speedup compared to the serial gridfree octree DSMC simulation.

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Gridless DSMC

Cited by 28 publications

References 42 publications

pdFOAM: A PIC-DSMC code for near-Earth plasma-body interactions

pdFOAM: A PIC-DSMC code for near-Earth plasma-body interactions

Properties of the solutions of delocalised coagulation and inception problems with outflow boundaries

A Hybrid CPU-GPU Parallel Octree Direct Simulation Monte Carlo Approach

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