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A parallelized three-dimensional self-consistent electrostatic particle-in-cell (PIC) code using unstructured tetrahedral mesh is proposed. Parallel implementation of the current unstructured PIC-FEM code is realized on distributed-memory PC-cluster system utilizing dynamic domain decomposition. Completed code is verified by simulating a quasi-1D RF argon gas discharge with results comparable to previous experimental observations and simulations. Parallel performance with dynamic domain decomposition of the PIC code is tested using a 3D RF argon gas discharge on a PC-cluster system. Results show that parallel efficiency can achieve 83% at 32 processors with dynamic domain decomposition. Some possible improvement of the code performance is demonstrated. Completed code is then applied to predict field emission without and with space-charge effect, and to simulate the RF magnetron argon plasma to demonstrate its capability in handling practical problems. [Copyright &y& Elsevier]

Abstract: In this paper, a true-direction flux reconstruction of the second-order quiet direct simulation (QDS-2N) Smith et al. (2009) [3] as an equivalent Euler equation solver, called QDS-N2, is proposed. Because of the true-directional nature of QDS, where volume-to-volume (true-direction) fluxes are computed, as opposed to fluxes at cell interfaces as employed by traditional finite volume schemes, a volumetric reconstruction is required to reach a totally true-direction scheme. The conserved quantities are permitted to vary (according to a polynomial expression) across all simulated dimensions. Prior to the flux computation, QDS particles are introduced using properties based on weighted moments taken over the polynomial reconstruction of the conserved quantity fields. The resulting flux expressions are shown to exactly reproduce the existing second-order extension for a one-dimensional flow, while providing a means for true multi-dimensional reconstruction. The new reconstruction is demonstrated in several verification studies. These include a shock–bubble interaction problem, an Euler-four-shock interaction problem, and the advection of a vortical disturbance. These results are presented, and the increased computation time and the effect of higher-order extension are discussed in this paper. The results show that the proposed multi-dimensional reconstruction provides a significant increase in the accuracy of the solution. We show that, despite the increase in the computational expense, the computational speed of the proposed QDS-N2 method is several times higher than that of the previously proposed QDS-2N scheme for a fixed degree of numerical accuracy, at least, for the test problem of the advection of vertical disturbances. [Copyright &y& Elsevier]

Abstract: Development of a hybrid numerical algorithm which couples weakly with the gas flow model (GFM) and the plasma fluid model (PFM) for simulating an atmospheric-pressure plasma jet (APPJ) and its acceleration by two approaches is presented. The weak coupling between gas flow and discharge is introduced by transferring between the results obtained from the steady-state solution of the GFM and cycle-averaged solution of the PFM respectively. Approaches of reducing the overall runtime include parallel computing of the GFM and the PFM solvers, and employing a temporal multi-scale method (TMSM) for PFM. Parallel computing of both solvers is realized using the domain decomposition method with the message passing interface (MPI) on distributed-memory machines. The TMSM considers only chemical reactions by ignoring the transport terms when integrating temporally the continuity equations of heavy species at each time step, and then the transport terms are restored only at an interval of time marching steps. The total reduction of runtime is 47% by applying the TMSM to the APPJ example presented in this study. Application of the proposed hybrid algorithm is demonstrated by simulating a parallel-plate helium APPJ impinging onto a substrate, which the cycle-averaged properties of the 200th cycle are presented. The distribution patterns of species densities are strongly correlated by the background gas flow pattern, which shows that consideration of gas flow in APPJ simulations is critical. [Copyright &y& Elsevier]

Abstract: In this paper, the development of a two-dimensional plasma fluid modeling code using the cell-centered finite-volume method and its parallel implementation on distributed memory machines is reported. Simulated discharge currents agree very well with the measured data in a planar dielectric barrier discharge (DBD). Parallel performance of simulating helium DBD solved by the different degrees of overlapping of additive Schwarz method (ASM) preconditioned generalized minimal residual method (GMRES) for different modeling equations is investigated for a small and a large test problem, respectively, employing up to 128 processors. For the large test problem, almost linear speedup can be obtained by using up to 128 processors. Finally, a large-scale realistic two-dimensional DBD problem is employed to demonstrate the capability of the developed fluid modeling code for simulating the low-temperature plasma with complex chemical reactions. [Copyright &y& Elsevier]

Analysis of the electrostatic characteristics and the gate capacitance of typical nanostructured carbon nanotube field effect transistors (CNTFETs) were performed numerically. A previously developed parallelized electrostatic Poisson''s equation solver (PPES) is employed, coupled with a parallel adaptive mesh refinement (PAMR) to improve the numerical accuracy near the region where variation of potentials are significant. CNTFETs with four typical configurations of the gate electrode, the bottom gate (BG), the double gate (DG), the top gate (TG), and the surrounding gate (SG) were simulated. Effects of the nanotube arrangement and the gate length on the gate capacitance are presented and discussed. The simulation results show that SG-CNTFET possesses the largest gate capacitance among various structures. However, TG-CNTFET is recommended for practical applications by taking into account both the device performance and the difficulty of fabrication. According to the simulated gate capacitance, estimation of the on-state current of CNTFETs is possible. [Copyright &y& Elsevier]

Abstract: The development of a parallel three-dimensional (3-D) adaptive mesh refinement (PAMR) scheme for an unstructured tetrahedral mesh using dynamic domain decomposition on a memory-distributed machine is presented in detail. A memory-saving cell-based data structure is designed such that the resulting mesh information can be readily utilized in both node- or cell-based numerical methods. The general procedures include isotropic refinement from one parent cell into eight child cells and then followed by anisotropic refinement which effectively removes hanging nodes. A simple but effective mesh-quality control mechanism is employed to preserve the mesh quality. The resulting parallel performance of this PAMR is found to scale approximately as for . Two test cases, including a particle method (parallel DSMC solver for rarefied gas dynamics) and an equation-based method (parallel Poisson–Boltzmann equation solver for electrostatic field), are used to demonstrate the generality of the PAMR module. It is argued that this PAMR scheme can be applied in any numerical method if the unstructured tetrahedral mesh is adopted. [Copyright &y& Elsevier]

Abstract: A parallel electrostatic Poisson''s equation solver coupled with parallel adaptive mesh refinement (PAMR) is developed in this paper. The three-dimensional Poisson''s equation is discretized using the Galerkin finite element method using a tetrahedral mesh. The resulting matrix equation is then solved through the parallel conjugate gradient method using the non-overlapping subdomain-by-subdomain scheme. A PAMR module is coupled with this parallel Poisson''s equation solver to adaptively refine the mesh where the variation of potentials is large. The parallel performance of the parallel Poisson''s equation is studied by simulating the potential distribution of a CNT-based triode-type field emitter. Results with ∼100 000 nodes show that a parallel efficiency of 84.2% is achieved in 32 processors of a PC-cluster system. The field emission properties of a single CNT triode- and tetrode-type field emitter in a periodic cell are computed to demonstrate their potential application in field emission prediction. [Copyright &y& Elsevier]

Abstract: The effect on the selection of different plasma chemistries for simulating a typical dielectric barrier discharge (DBD) driven by quasi-pulsed power source (20 kHz) is investigated. The numerical simulation was performed by using the one-dimensional self-consistent fluid modeling solver. Our simulation result indicates that the computed temporal current density can be significantly improved by using a complex version of plasma chemistry module rather than the simple one and demonstrates an excellent agreement with the experimental data. The result suggests the metastable, excited and ionic helium related reaction channels, which are important in simulating a DBD, should be taken into account. Furthermore, it also reveals that the power absorption of ions is considerably higher than that of the electron. [Copyright &y& Elsevier]

Abstract: Parallel-plate nitrogen dielectric barrier discharge (DBD) driven by a quasi-pulsed power source (60 kHz) is simulated using a fully-implicit 1D self-consistent fluid modeling code. Simulated discharged currents of gap distances (0.5, 0.7 and 1.0 mm) agree very well with measured data; while simulated discharged currents of wider gap distance (1.2 mm) fail to reproduce the measured data. It is found that the discharge mode is homogeneous Townsend-like for the former case; while it is filamentary-like for the latter case based on the experimental observation. These findings demonstrate that previous numerical studies showing mode transition by changing the gap distance may require further investigation. [Copyright &y& Elsevier]

Abstract: Interaction of femto-second pulsed laser with a nitrogen molecule at various angles is investigated numerically in the present study. We propose a three-dimensional time-dependent Schrödinger equation (TDSE) solver using finite volume method (FVM) with single-active-electron (SAE) assumption. We construct the model potential by combining the soft-Coulomb potential and Yukawa potential and fitting both the first ionization energy and orbital type of highest-occupied molecular orbital (HOMO) of a N2 molecule. The ratio of simulated maximum () to minimum () ionization yield is 1.9 and it agrees more favorably with the converted experimental data (2.3–3.3) than the MO-ADK model does (10.0). This shows that the proposed model potential in the 3D TDSE solver can faithfully predict the ionization of a nitrogen molecule under strong pulsed laser incidence and is a very useful tool for future application in similar analysis of more complicated molecules. [Copyright &y& Elsevier]