Browsing by Author "Kuo, T. C."

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Implementation of a transient adaptive sub-cell module for the parallel-DSMC code using unstructured grids
(2010-08-01)
Su, C. C.
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Tseng, K. C.
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Cave, H. M.
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Wu, J. S.
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Lian, Y. Y.
A method of transient adaptive sub-cells (TAS) suitable for unstructured grids that is modified from the existing one for the structured grids of DSMC is Introduced. The TAS algorithm is implemented within the framework of a parallelized DSMC code (PDSC). Benchmarking tests are conducted for steady driven cavity flow, steady hypersonic flow over a two-dimensional cylinder, steady hypersonic flow over a cylinder/flare and the unsteady vortex shedding behind a two-dimensional cylinder The use of TAS enables a reduction in the computational expense of the simulation since larger sampling cells and less simulation particles can be employed. Furthermore, the collision quality of the simulation is maintained or improved and the preservation of property gradients and vorticity at the scale of the sub-cells enables correct unsteady vortex shedding frequencies to be predicted The use of TAS in a parallel-DSMC code allows simulations of unsteady processes at a level to be carried out efficiently, accurately and with acceptable computational time (C) 2010 Elsevier Ltd All rights reserved
Implementation of the Transient Adaptive Sub-Cell Module for the Parallel DSMC Code
(2009)
Tseng, K. C.
;
Cave, H. M.
;
Kuo, T. C.
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Jermy, M. C.
;
Krumdieck, S. P.
A method of transient adaptive sub-cells (TAS) suitable for unstructured grids in Direct Simulation Monte Carlo (DSMC) simulations is introduced. The TAS algorithm is implemented within the frame work of a parallelized DSMC code (PDSC). Benchmarking tests are conducted for driven cavity (low, hypersonic flow over a two-dimensional cylinder and the unsteady vortex shedding behind a two-dimensional cylinder. The use of TAS enabled a reduction in the computational expense of the simulation since larger sampling cells and less simulation particles could be employed. Furthermore, the collision quality of the simulation was maintained or improved and the preservation of property gradients and vorticity at the scale of the sub-cells enabled correct unsteady vortex shedding frequencies to be predicted. The use of TAS in a parallel DSMC code allows simulations of unsteady processes at a near continuum level to be carried out efficiently, accurately and with acceptable computational times.
Simulations of subsonic vortex-shedding flow past a 2D vertical plate in the near-continuum regime by the parallelized DSMC code
(2012-08-01)
Tseng, K. C.
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Kuo, T. C.
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Lin, S. C.
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Su, C. C.
;
Wu, J. S.
A general-purpose Parallel Direct Simulation Monte Carlo Code, named PDSC, is used to simulate near-continuum subsonic flow past a 2D vertical plate for studying the vortex-shedding phenomena. An unsteady time-averaging sampling method and a post-processing procedure called DREAM (DSMC Rapid Ensemble Averaging Method) have also been implemented, reducing the overall computational expense and improving the sampling quality of time-dependent flow problems in the rarefied flow regime. Parametric studies, including the temporal variable time step (TVTS) factor, the number of particles per cell, the domain size, and the Reynolds number, have been conducted, obtaining the Strouhal number and various aerodynamic coefficients of the flow. Results are compared to experimental data in the continuum regime available in the literature, demonstrating the capacity of PDSC and DREAM to simulate near-continuum vortex-shedding problems within acceptable computational time. (C) 2012 Elsevier B.V. All rights reserved.