Browsing by Author "Lin, K. -M."

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A parallel hybrid numerical algorithm for simulating gas flow and gas discharge of an atmospheric-pressure plasma jet
(2012-12-01)
Lin, K. -M.
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Hu, M. -H.
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Hung, C. -T.
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Wu, J. -S.
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Hwang, F. -N.
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. (C) 2012 Elsevier B.V. All rights reserved.
Development of an improved spatial reconstruction technique for the HLL method and its applications
(2011-02-01)
Smith, Matthew R.
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Lin, K. -M.
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Hung, C. -T.
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Chen, Y. -S.
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Wu, J. -S.
The integral form of the conventional HLL fluxes are presented by taking integrals around the control volume centred on each cell interface. These integrals are demonstrated to reduce to the conventional HLL flux through simplification by assuming spatially constant conserved properties. The integral flux expressions are then modified by permitting the analytical inclusion of spatially linearly varying conserved quantities. The newly obtained fluxes (which are named HLLG fluxes for clarification, where G stands for gradient inclusion) demonstrate that conventional reconstructions at cell interfaces are invalid and can produce unstable results when applied to conventional HLL schemes. The HLLG method is then applied to the solution of the Euler Equations and Shallow Water Equations for various common benchmark problems and finally applied to a 1D fluid modeling for an argon RF discharge at low pressure. Results show that the correct inclusion of flow gradients is shown to demonstrate superior transient behavior when compared to the existing HLL solver and conventional spatial reconstruction without significantly increasing computational expense. (C) 2010 Elsevier Inc. All rights reserved.
Numerical Investigation of a Parallel-Plate Atmospheric-Pressure Nitrogen/Ammonia Dielectric Barrier Discharge
(2012-06-01)
Li, F. -L.
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Lin, K. -M.
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Yang, Y. -W.
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Hung, C. -T.
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Wu, J. -S.
In this paper, a planar atmospheric-pressure dielectric barrier discharge (AP-DBD) of nitrogen mixed with ammonia (0-2 %) is simulated using one-dimensional self-consistent fluid modeling with cell-centered finite-volume method. This AP-DBD is driven by a 30 kHz power source with distorted sinusoidal voltages. The simulated discharge current densities are found to be in good agreement with the experiment data in both phase and magnitude. The simulated results show that the discharges of N-2 mixed with NH3 (0-2 %) are all typical Townsend-like discharges because the ions always outnumber the electrons very much which leads to no quasi-neutral region in the gap throughout the cycle. N-2 (+) and N-4 (+) are found to be the most abundant charged species during and after the breakdown process, respectively, like a pure nitrogen DBD. NH4 (+) increases rapidly initially with increasing addition of NH3 and levels off eventually. In addition, N is the most dominant neutral species, except the background species, N-2 and NH3, and NH2 and H are the second dominant species, which increase with increasing added NH3. The existence of abundant NH2 plays an important role in those applications which require functional group incorporation.