Browsing by Author "Lian, Y. Y."

Now showing 1 - 4 of 4

Implementation of a transient adaptive sub-cell module for the parallel-DSMC code using unstructured grids
(2010-08-01)
Su, C. C.
;
Tseng, K. C.
;
Cave, H. M.
;
Wu, J. S.
;
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
Mixing Effectiveness Study in Scramjet Combustion
(2013-01-01)
Chen, Y. S.
;
Lian, Y. Y.
;
Chou, T. H.
;
Lai, Alfred
;
Wu, J. S.
Scramjet propulsion provides promising opportunities for high-speed transportation and cost reduction for satellite and spacecraft launch operations. This paper provides some selected numerical examples among the abundance of available test cases for the purpose of demonstrating to what extends the current computational models can do in assisting the design and test programs of scramjet combustors. Numerical examples that cover a wide range of flight speeds are investigated with benchmark data validations. Ideas of mixing enhancement and flame holding mechanisms in scramjet combustion is analyzed and planned for the future experimental investigations. (C) 2013 The Authors. Published by Elsevier Ltd.
Multiphysics simulations of rocket engine combustion
(2011-06-01)
Chen, Yen-Sen
;
Chou, T. H.
;
Gu, B. R.
;
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.
Two-level virtual mesh refinement algorithm in a parallelized DSMC Code using unstructured grids
(2011-09-01)
Su, C. C.
;
Tseng, K. C.
;
Wu, J. S.
;
Cave, H. M.
;
Jermy, M. C.
In this paper, a virtual mesh refinement (VMR) algorithm for unstructured grids is developed and verified in the parallelized direct simulation Monte Carlo code (PDSC). This algorithm is a two-level virtual mesh refinement, in which the background mesh is refined based on an initial DSMC simulation. The refined cells are arranged in a way similar to the structured grid, which makes the particle tracing on them very efficient, unlike unstructured grids. These virtual cells are used for particle collision and sampling. Only those refined cells which contain the centroid of background cells are used for outputting macroscopic data. Two hypersonic flows with purely quadrilateral and mixed triangular-quadrilateral mesh were used to verify this new mesh-refining algorithm. Results show that the case using VMR can faithfully reproduce the benchmark case with a much reduced computational time. (C) 2011 Elsevier Ltd. All rights reserved.