• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.518-521
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• 2008

When constructing a high-speed railroad, the reduction of the distance between track centers and the width of track bed will save the construction cost. However the shortening the distance between track centers may cause the stability problems due to higher wind pressure. Therefore the extensive technical review and aerodynamical study should be performed to determine the adequate distance between track centers. In this study, the impact that the increase in wind pressure due to the change of aerodynamic phenomena with the change of the distance between track centers may have on two trains passing by each other was predicted, and the stability of train operation was analyzed in order to review the distance between track centers suitable to Honam HSR trains. And we estimated the aerodynamical effects by the results of the real train experiments by using KTX.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.33.1-33.1
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• 2011

풍력발전기가 점차 대형화되어가는 추세에 따라 블레이드 역시 점차 길어지고 무거워지는 경향을 보이고 있다. 이는 블레이드뿐만 아니라 풍력발전기 시스템 전체의 하중 및 비용의 증가를 불러오게 되므로, 시스템의 성능 및 하중에 가장 큰 영향을 끼치는 블레이드의 공력특성에 대한 연구가 전 세계적으로 지속되고 있다. 그 중에서도 특히 작동 중 오염에 의한 블레이드 표면 거칠기 변화는 블레이드의 공력특성을 변화시켜, 발전기 전체의 성능뿐만 아니라 전체 하중에도 영향을 끼치는 주요 인자이다. 따라서 풍력발전기 블레이드 설계 시에 예측된 설계하중과 실제 운용 환경에 의해 변화된 운용하중 간의 차이를 예측할 수 있다면, 블레이드 설계 시에 표면 거칠기 변화에 따른 영향을 고려함으로써 실제 운용 환경에 맞는 최적의 블레이드 및 풍력발전기 시스템 설계를 수행할 수 있다. 본 연구에서는 블레이드의 표면 거칠기 변화에 따라 풍력발전기 하중이 어떻게 영향을 받는지에 대하여 분석하였다. 이를 위하여 표면 거칠기 민감도를 고려하지 않고 설계된 기준 블레이드와, 운용 중 표면 거칠기가 변화된 블레이드의 2개 모델에 대한 하중해석을 수행하고 그 결과를 비교하였다. 보다 실제적인 해석을 위해 Multi-MW 급 풍력발전기 시스템 모델을 대상으로 최적 설계된 블레이드를 기준 모델로 삼았다. 하중계산방법은 IEC 및 GL 2010 가이드라인을 참고하였으며, 일부 주요 극한하중 상황에 대하여 해석을 수행하여 설계하중상황(design load case, DLC) 별로 하중의 증감 및 경향을 비교하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.4
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• pp.269-275
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• 2017

The aeroelastic stability of a fighter type aircraft can be severly affected by the store mass, aerodynamic characteristics, and store combinations. Hence, the stability for the all store configurations must be substantiated before the aircraft in service. For the aeroelastic analysis, the design data and information for the aircraft structure, mass distribution, control surface characteristics, and external shape etc. are required. This is the reason that the store compatibility substantiations by a third party are restricted. However, according to the change of operational environment or the improvement of avionic technology, a new external store is developed and it should be installed on an aircraft without the support from the original supplier. This paper describe the process to substantiate the aeroelastic compatibility between a new external store and an imported aircraft whose design data is not available to a third party operating the aircraft.

• Journal of the Korean Society for Railway
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• v.12 no.1
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• pp.39-44
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• 2009

The ballast-flying, induced by strong underbody flow of high-speed train, can damage train underbody, wheel and even cause the safety problems. For this reason, a heighter is being used to prevent ballast-flying through underbody flow reduction. In this research, flow field around a heighter is numerically simulated.. And the parametric study of various heighter geometries is performed to find out more effective heighter shape. Through these numerical studies, the relation between the heighter shape and underbody flow is found out. Also new heighter shapes are numerically investigated and their performances of underbody flow reduction are verified.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.1
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• pp.20-27
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• 2002

Aircraft design requires the intergration of several disciplines, inculding aerodynamics, structures, controls. To achieves advances in performance, each technology, or discipline must be more accurate in analysis and must be more highly intergrated. One of the important interdisciplinary interactions in mordern aircraft design is that of aerodynamics and structures. In this study, for increasing accuracy in each discipline's analysis, CFD for aerodynamic analysis and FEM for structurral analysis was used and, for considering important interdisciplinary interactions, aeroelastic effect was considered. As optimization algorithm, PBIL algorithm was used for global optima and was parallelized to alleviate the computational burden. The efficiency and accuracy of the present method was assesed by range maximiziation of reference of reference wing.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.11
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• pp.971-977
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• 2015

A numerical analysis for the performance of compound gyroplane in forward flight was performed. TSM(Transient Simulation Method) was used to analyze the performance of autorotating rotor. CFD was conducted for the fuselages to recognize the variation of aerodynamic performance according to flight speed. At given conditions; airspeed, shaft angle and collective pitch, the quasi-static states of autorotation were determined and the variation of rotor performance was observed. Performance analysis results showed that the effect of aerodynamic characteristics in accordance with the shape of fuselage is so important that the streamlined fuselage is essential to fly fast. Forward flight speed limit is dependent on the autorotation performance of rotor.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.3
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• pp.167-174
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• 2021

Computational Fluid Dynamics (CFD) was performed under low-speed wind tunnel test conditions using a 29.7% scale model of the NASA common research model. A wind tunnel test was conducted to measure the aerodynamic coefficient of the CRM with Belly sting model support configuration at a low Reynolds number of 0.3×106 and it was compared with the aerodynamic coefficient of CFD analysis. In order to verify the validation of the analysis, a computational analysis under the conditions of the advance research was performed and compared. The interference effect of the Belly sting model support affected not only the fuselage but also the main and tail wings.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.5A
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• pp.341-349
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• 2011

The main purpose of this study is to investigate the affect of various turbulence properties on aerodynamic characteristics of twin box bridge section. To achieve this goal, active turbulence generator which successfully simulated various target turbulences was developed in the wind tunnel. From the wind tunnel tests, turbulence integral length scale did not affect on the aerodynamic forces and flutter derivatives except for the $A_1^*$ curve. Turbulence intensity gave slight effect on the unsteady aerodynamic force, but turbulence integral length scale did not affect the self-excited forces except vertical direction component.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.7
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• pp.621-627
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• 2008

Aerodynamic data measured in a wind tunnel has inevitable errors due to the presence of the wind tunnel walls. These unwanted interference effects must be corrected for the wall interference free aerodynamic data. Streamline curvature effects are caused by straightening of streamlines due to wind tunnel walls. Classical Glauert's correction method that is a standard method for fixed wing aircraft is not suitable for rotary wing aircraft. In this paper, Heyson's correction method of which wake model is compatible with rotors is used to correct the rotor shaft angle as well as the dynamic pressure. The results of Heyson's method are compared with Glauert's correction method.

• Journal of Aerospace System Engineering
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• v.9 no.3
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• pp.12-16
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• 2015

인간동력 항공기 TORUK MAKTO I에 대하여 양력선이론 및 XFOIL을 사용하여 도출한 공력계수 및 미계수 값과 CATIA를 사용한 관성모멘트 추정 값을 사용하여 지면효과 및 주익과 무게중심 사이의 수직거리 변화가 인간동력 항공기의 세로 정안정성에 미치는 영향과 수평미익(스테빌레이터) 변위각제어에 따른 세로 동안정성 해석 연구를 수행하였다. 연구결과 지면효과가 정적여유에 미치는 영향은 미미했다. 공력중심과 무게중심 사이의 수직거리가 세로 정안정성에 미치는 영향은 매우 컸으며, 수직거리 증가는 세로 정안정성을 증가시켰다. 수평미익 변위각 제어에 따른 세로 동안정성 해석 결과 장주기 진동특성과 감쇄특성이 매우 나쁜 것으로 나타났다. 향후 항공기의 동특성을 고려한 세로 동안정성 해석 및 측풍에 의한 가로 및 방향 안정성 해석연구를 수행할 예정이다.