Suchergebnisse

The present paper deals with a vortex generator source model for the adjoint-based design optimization. To efficiently design the vortex generator inside an S-shaped subsonic inlet, the vortex generator source model is employed instead of the fully gridded vortex generator. The previously developed original source model, however, does not reflect a small change in position and thus has difficulties in differentiation for sensitivity analysis. For this reason, the original source model is modified into a differentiable source model. Through the differentiable source model, a large number of design variables including vortex generator position can be treated with an adjoint variable method. After the optimization with the design variables of the chord length, height, angle of incidence, axial and circumferential positions of each vortex generator, the performance of the target inlet is remarkably improved, showing that the distortion coefficient well over 70% while maintaining the total pressure recovery ratio. ; This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (No. 2011-0027486). ; OAIID:oai:osos.snu.ac.kr:snu2012-01/104/0000004648/16 ; SEQ:16 ; PERF_CD:SNU2012-01 ; EVAL_ITEM_CD:104 ; USER_ID:0000004648 ; ADJUST_YN:N ; EMP_ID:A001138 ; DEPT_CD:446 ; CITE_RATE:0 ; FILENAME:IMPROVEMENT_OF_VORTEX_GENERATOR_SOURCE_MODEL_FOR_ADJOINT-BASED_DESIGN_OPTIMIZATION.pdf ; DEPT_NM:기계항공공학부 ; EMAIL:chongam@snu.ac.kr ; CONFIRM:Y

A fluid-structure interaction of solid propellant rocket interior is carried out by employing the ALE (Arbitrary Lagrangian Eulerian) description, a hybrid model of continuum motion description combining the advantages of classical Lagrangian and Eulerian description. The fluid-structure interaction process and an automatic re-meshing algorithm are included to analyze an unsteady fluid-structure interaction phenomenon with the deformation of solid grain during the simulation. The developed solver is applied for the full burning simulation of a solid propellant grain, which is a highly-coupled unsteady phenomenon between gas flow and propellant structure. Based on the integrated computed results, flow physics in the combustion chamber and the behavior of a solid propellant deformation are examined. ; Authors appreciate the financial supports provided by NSL (National Space Lab.) program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (Grant 2011-0029871) and by National Institute for Mathematical Sciences (NIMS) grant funded by the Korea government (No. A21001). ; OAIID:oai:osos.snu.ac.kr:snu2012-01/104/0000004648/17 ; SEQ:17 ; PERF_CD:SNU2012-01 ; EVAL_ITEM_CD:104 ; USER_ID:0000004648 ; ADJUST_YN:N ; EMP_ID:A001138 ; DEPT_CD:446 ; CITE_RATE:0 ; FILENAME:ALE-BASED_FSCI_COMPUTATIONS_FOR_SOLID_ROCKET_INTEIOR.pdf ; DEPT_NM:기계항공공학부 ; EMAIL:chongam@snu.ac.kr ; CONFIRM:Y

The present paper deals with the continuous work of extending multi-dimensional limiting process (MLP) for higher-order discontinuous Galerkin (DG) methods to compute compressible Navier-Stokes equation. From the previous works, it was observed that the MLP shows several superior characteristics, such as efficient controlling of multi-dimensional oscillations and accurate capturing of complex flow structure. Recently, MLP has been extended into DG method for hyperbolic conservation laws. The proposed method, called hierarchical MLP, can be readily extended to convection-dominated problem, such as compressible Navier-Stokes equation. Through several test cases, it is observed that that the proposed approach yields outstanding performances in resolving non-compressive as well as compressive viscous flow features. ; Authors appreciate the financial supports provided by NSL (National Space Lab.) program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (Grant 2011-0029871), by the KISTI Supercomputing Center (KSC- 2010-C1-0031) and by National Institute for Mathematical Sciences (NIMS) grant funded by the Korea government (No. A21001). ; OAIID:oai:osos.snu.ac.kr:snu2012-01/104/0000004648/18 ; SEQ:18 ; PERF_CD:SNU2012-01 ; EVAL_ITEM_CD:104 ; USER_ID:0000004648 ; ADJUST_YN:N ; EMP_ID:A001138 ; DEPT_CD:446 ; CITE_RATE:0 ; FILENAME:HIERARCHICAL_MULTI-DIMENSIONAL_LIMITING_STRATEGY_ON_DG_DISCRETIZATION.pdf ; DEPT_NM:기계항공공학부 ; EMAIL:chongam@snu.ac.kr ; CONFIRM:Y

The present paper deals with the continuous work of extending multi-dimensional limiting process (MLP) for high speed compressible flows (or hyperbolic conservation laws), which has been quite successful in finite volume method (FVM), into discontinuous Galerkin (DG) methods. Based on successful analyses and implementations of the MLP slope limiting in FVM, MLP is applicable into DG framework with the MLP-based troubled-cell marker and the MLP slope limiter. Through several test cases, it is observed that the newly developed DG-MLP methods provide quite desirable performances in controlling numerical oscillations as well as capturing key flow features. ; Authors appreciate the financial supports provided by NSL (National Space Lab.) program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (Grant 20090091724), by National Institute for Mathematical Sciences (NIMS) grant funded by the Korea government (No. A21001), Ministry of Land, Transport and Maritime Affairs (MLTM) through the Super Long Span Bridge R&D Center in Korea. ; OAIID:oai:osos.snu.ac.kr:snu2010-01/104/0000004648/41 ; SEQ:41 ; PERF_CD:SNU2010-01 ; EVAL_ITEM_CD:104 ; USER_ID:0000004648 ; ADJUST_YN:N ; EMP_ID:A001138 ; DEPT_CD:446 ; CITE_RATE:0 ; FILENAME:DISCONTINUOUS_GALERKIN-MLP_METHODS_FOR_COMPRESSIBLE_FLOW_ANALYSES.pdf ; DEPT_NM:기계항공공학부 ; EMAIL:chongam@snu.ac.kr ; CONFIRM:Y

In Korea, prospective college students are increasingly avoiding natural science and engineering. Government is trying to develop an information communication technology (ICT) infrastructure contributed to the encouragement of learner-centered education and to the qualitative enhancement of academic research. It also contributed to the increase in the use of ICT in various areas and to the remarkable improvement in the level of information utilization. In this paper, we introduce a cyber education system for aerospace engineering, which is named e-AIRS. e-AIRS, an abbreviation of 'e-Science Aerospace Integrated Research System', is a cyber-infrastructure based portal system to support the aerodynamics engineering processes on the e-Science environment. The web portal interface is implemented as a portlet component model on top of the Gridsphere Framework, and these portlets can be reusable. The system provides CFD simulations, remote experimental service, and collaborative and integrative study between computation and experiment through the web. The system helps students to understand the full simulation process of aerodynamics engineering. We conducted a survey of about 150 students at the Seoul National University and Konkuk University in Korea. According to the survey, 94 percent said the system helped to understand the whole process of CFD, and more than 90 percent of the students said e-AIRS portal provided a good functionality, convenience, and user interface. ; OAIID:oai:osos.snu.ac.kr:snu2008-01/104/0000004648/57 ; SEQ:57 ; PERF_CD:SNU2008-01 ; EVAL_ITEM_CD:104 ; USER_ID:0000004648 ; ADJUST_YN:N ; EMP_ID:A001138 ; DEPT_CD:446 ; CITE_RATE:0 ; FILENAME:CFD Cyber Education Service using Cyberinfrastructure for e-Science.pdf ; DEPT_NM:기계항공공학부 ; EMAIL:chongam@snu.ac.kr ; CONFIRM:Y

The existing computer code to solve the airflow in a segmented constrictor-type arc-heated wind tunnel named ARCFLO4 is improved to accept an air–argon mixture as the working gas. The new version of the code is used to calculate the flows in the Aerodynamic Heating Facility of NASA Ames Research Center where argon concentration is relatively high. The calculation shows that argon tends to increase the diameter of the arc column, increase ionization fraction, decrease thermal efficiency of the arc heater, and push the ratio of the centerline-to-average enthalpy toward unity. The calculated operating characteristics of the arc heater agree well with the experimental data and the results of the calculations made by Sakai using a similar code developed earlier, ARCFLO3. ; This work was supported by the Korea Research Foundation Grant funded by the Korean Government (Ministry of Education&Human Resources Development, Basic Research Promotion Fund) (KRF- 2006-331-D00089). The authors appreciate the financial support from the Brain Korea 21 Project. The authors would like to acknowledge the support from KISTI (Korea Institute of Science and Technology Information) Supercomputing Center (KSC-2007-S00- 1015).

This paper presents a transient time aeroelastic analysis for a supersonic flight vehicle with a ramjet engine. First, computational fluid dynamics (CFD) is conducted to estimate its baseline geometry and the prediction results obtained upon the vehicle surface are transferred to the structural transient time analysis. The structural analysis is then carried out. A brand new finite element domain decomposition structure analysis is developed for the present transient time aeroelastic analysis. To solve a resulting large-scale system equation, FETI method is adopted for the present shell analysis. And comparison results between the present transient time FETI and Dual-primal FETI methods are attempted. During the 500 time steps, both analyses show good agreement with a difference less than 0.01% for the example problem. As a result, a detailed analytical procedure for the transient time aeroelastic analysis is established to predict a possibility of an excessive deformation or buckling induced in the supersonic vehicle during flight. ; This work was supported by the Korea Research Foundation Grant funded by the Korean Government (MOEHRD, Basic Research Promotion Fund) (KRF-2008-331-D00098). And, it was also supported by the New and Renewable Energy Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Knowledge Economy (No.20104010100490). ; OAIID:oai:osos.snu.ac.kr:snu2012-01/104/0000004648/40 ; SEQ:40 ; PERF_CD:SNU2012-01 ; EVAL_ITEM_CD:104 ; USER_ID:0000004648 ; ADJUST_YN:N ; EMP_ID:A001138 ; DEPT_CD:446 ; CITE_RATE:0 ; FILENAME:6.2012-3271.pdf ; DEPT_NM:기계항공공학부 ; EMAIL:chongam@snu.ac.kr ; CONFIRM:Y