Browsing by Author "Yang, Luke"

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Improved parallelized hybrid DSMC-NS method
(2011-06-01)
Lian, Yu-Yung
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Chen, Yen-Sen
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Tseng, K. -C.
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Wu, J. -S.
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Wu, Bill
In this paper, an improved parallelized hybrid DSMC-NS (Navier-Stokes method) algorithm, as compared to the previous work [1], is presented. A detailed kinetic velocity sampling study is conducted with a two-dimensional supersonic flow (M(infinity) = 4) past a 25 degrees finite wedge. It shows most of the boundary layer region is in nearly thermal equilibrium, even with very high continuum breakdown parameter based on velocity, velocity gradient and local mean free path. A new continuum breakdown parameter based on pressure is designed to effectively "exclude" the "false" breakdown region such as the boundary layer. An improved hybrid DSMC-NS algorithm is verified using the same wedge flow case. Results show that the improved algorithm can greatly reduce the computational cost while maintaining essentially the same accuracy. A hypersonic flow (M(infinity) = 12) past a square cylinder is also employed to exhibit the capability of the improved hybrid DSMC-NS method. (C) 2010 Elsevier Ltd. All rights reserved.
Multiphysics simulations of rocket engine combustion
(2011-06-01)
Chen, Yen-Sen
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Chou, T. H.
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Gu, B. R.
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Wu, J. S.
;
Wu, Bill
Recently, the hybrid rocket propulsion has become attractive to the research community and has developed the trend to become an alternative to the conventional liquid and solid rockets. The hybrid rocket is a combination of both the solid and liquid systems with half of the plumbing of the liquid rocket but retaining its operational flexibility and avoiding the explosive nature of the solid rocket. Among available hybrid systems, the N(2)O (Nitrous Oxide)-HTPB (Hydroxyl-Terminated PolyButadiene) hybrid propulsion represents the simplest but sufficiently efficient design. Unfortunately, even until now, research in developing hybrid N(2)O-HTPB propulsion system still strongly depends on trials-and-errors, which are time-consuming and expensive. Thus, detailed understanding of the fundamental combustion processes that are involved in the N(2)O-HIPB propulsion system can greatly impact the research community in this field. This may further facilitate the successful modeling of the combustion processes and help improving the design of N(2)O-HTPB propulsion system in the future. A comprehensive numerical model with real-fluid properties and finite-rate chemistry was developed in this research to predict the combustion flowfield inside a N(2)O-HIPB hybrid rocket system. Good numerical predictions as compared to experimental data are also presented. (C) 2010 Elsevier Ltd. All rights reserved.