• 항공우주시스템공학회지
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• 제16권2호
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• pp.25-32
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• 2022

캡 루프 페어링은 상용차가 주행 시 전면부에서 발생하는 유동 박리의 저항을 제어하여 상용차 항력 계수를 줄이는 장치이다. 상용차는 구조적으로 후방의 컨테이너를 적재해야 되기 때문에 차량의 주행방향으로부터 공기역학적 저항력을 피할 수 없게 설계되어 있다. 이러한 이유 때문에 유류비, 환경오염물질과 밀접한 연관을 가진다. 본 연구에서는 랭킨 반체 이론을 바탕으로 3D 페어링 형상을 설계하고 공력 해석을 통해 설계 결과를 검증하였다.

• Wind and Structures
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• 제38권3호
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• pp.203-214
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• 2024

Large-span cantilevered roof represents a unique type of structure that is vulnerable to wind loads. Inspired by the need to maximumly reducing the rooftop wind loads, this study examined the feasibility of positioning vented slots on the leading edge, and the effectiveness of such aerodynamic mitigation measures are assessed via both physical and numerical simulations. The reliability of numerical simulation was evaluated via comparisons with the wind tunnel tests. The results indicated that, the variation of venting hole arrangement can cause significant change in the rooftop wind load characteristics. For the cases involved in this study, the maximum reduction of mean and peak wind suction coefficients are found to be 9% and 8% as compared to the original circular slot without venting holes. In addition, the effect of slot shape is also evident. It was shown that the triangular shaped slot tends to increase the wind suction near the leading edge, whereas the hexagonal and octagonal shaped slots are found to decrease the wind suction. In particular, with the installation of octagonal shaped slot, the maximum reduction of wind suction coefficients near the leading edge reaches up to 31% as compared to the circular shaped slot, while the maximum reduction of mean wind suction coefficients is about 30%.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.33-36
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• 2005

A critical issue in the field of the rotor aerodynamics is the treatment of the wake. The wake is of primary importance in determining overall aerodynamic behavior, especially, a wind turbine blade includes the unsteady air loads problem. In this study, the wake generated by blades are depicted by a free wake model to analyse unsteady loading on blade and a new free wake model named Finite Vortex Element(FVE hereafter) is devised in order to include a wake-tower interact ion. In this new free wake model, blade-wake-tower interaction is described by cutting a vortex filament when the filament collides with a tower. This FVE model is compared with a conventional free wake model and verified by a comparison with NREL and SNU wind tunnel model. A comparison with NREL and SNU data shows validity and effectiveness of devised FVE free wake model and an efficient.

• 한국전산유체공학회지
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• 제16권4호
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• pp.14-20
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• 2011

The initial unfolding motion simulation of a sub-munition with drag ribbon for precision guidance and reliable operation has been investigated by analyzing its unsteady aerodynamic load and fluid structure interaction. The effects of change in the ribbon configuration and flow angle are numerically studied using a commercial software "XFLOW" based on Lattice-Boltzmann Method. It is shown that the motion is affect adversely by the separation bubble formed posterior part of the fuselage. The rolling moment for arming of the sub-munition is increased with angle of attack and rotational movement.

• 한국소음진동공학회논문집
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• 제19권7호
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• pp.651-658
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• 2009

In this study, computer applied engineering(CAE) techniques are fully used to efficiently conduct structural and dynamic analyses of a huge composite rotor blade using super-element. Computational fluid dynamics(CFD) is used to predict aerodynamic loads of the rotating wind-turbine blade. Structural vibration analysis is conducted based on the non-linear finite element method for composite laminates and multi-body dynamic simulation tools. Various numerical results are presented for comparison and the structural dynamic behaviors of the rotor blade are investigated herein.

• International Journal of Aeronautical and Space Sciences
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• 제5권1호
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• pp.64-74
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• 2004

The Grid is a communication service that collaborates dispersed highperformance computers so that those can be shared and worked together. It enablesthe analysis of large-scale problem with the reduction of computation time bycollaborating high performance computing resources in dispersed organizations. Thus,the present paper focuses on the efficient flow calculation using the Grid. To increaseparallel efficiency, a simple load balance algorithm for the Grid computing is proposedand applied to various aerodynamic problems.

• 한국유체기계학회 논문집
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• 제17권4호
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• pp.11-18
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• 2014

The recent high speed propeller with blade sweep is required to have high strength to get the thrust to fly at high speed. The high stiffness and strength carbon/epoxy composite material is used for the major structure and skin-spar-foam sandwich structural type is adopted for advantage in terms of the blade weight. As a design procedure for the present study, the structural design load is estimated through investigation on aerodynamic load and then flanges of spars from major bending loads and the skin from shear loads are sized using the netting rule and Rule of Mixture. In order to investigate the structural safety and stability, stress analysis is performed by finite element analysis code MSC. NASTRAN. It is found that current methodology of composite structure design is a valid method through the static structural test of prototype blade.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2010년도 하계학술대회 논문집
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• pp.178-179
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• 2010

This paper presents a simulation model and analysis of grid-tied wind turbine generator with batteries using the PSCAD/EMTDC software. The modeled system is consist of two inverters and one bidirectional DC/DC converter. These inverter are to capture the maximum active power under varying wind conditions and to keep the DC-Link voltage magnitude at a specific level. And the bidirectional DC/DC converter makes battery charging or discharging depend on power gap between wind turbine output and local load. Aerodynamic models are applied for a wind turbine blade simulator.

• 항공우주기술
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• 제1권1호
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• pp.8-27
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• 2002

본 연구에서는 현재 개발중에 있는 복합재료 선미익 항공기의 날개에 작용하는 하중해석을 수행하였다. 중량, 공력계수, 구조설계속도, 하중 등을 계산하기 위해 사용된 Tool은 Excel에서 운용되는 Visual Basic 프로그램으로 계산에 많은 도움을 주었다. 하중해석에 기본적으로 요구되는 항공기의 형상치수, 부품의 종류 및 중량 그리고 좌표계 등은 Catia 모델링, 실제측정 또는 재료밀도 값 등을 이용해 구하였으며, 이들 자료를 통하여 항공기의 중량, 무게중심, 관성모멘트, 구조설계속도, 날개의 하중분포, 힘과 모멘트 등을 계산하였다. 또한 항공기의 날개 및 동체의 임계하중 조건을 선정하는데 필수적인 항공기의 V-n 선도를 도시하였으며, 이 V-n 선도는 항공기의 최대중량 2,573 파운드 및 해면고도조건에서 설계속도 $V_A$, $V_C$, $V_D$ 및 하중계수 +3.8G, -1.52G에 대한 비행범위를 제시하고 있다. 앞으로는 V-n 선도로부터 선정된 임계하중을 이용하여 해석된 동체 및 날개에 대한 하중을 제시하고자 한다.

• Wind and Structures
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• 제3권3호
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• pp.177-191
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• 2000

This paper presents an approach for evaluating directionality effects for both wind speeds and wind loads in hurricane-prone regions. The focus of this study is on directional wind loads on low-rise structures. Using event-based simulation, hurricane directionality effects are determined for an open-terrain condition at various locations in the southeastern United States. The wind speed (or wind load) directionality factor, defined as the ratio of the N-year mean recurrence interval (MRI) wind speed (or wind load) in each direction to the non-directional N-year MRI wind speed (or wind load), is less than one but increases toward unity with increasing MRI. Thus, the degree of conservatism that results from neglecting directionality effects decreases with increasing MRI. It may be desirable to account for local exposure effects (siting effects such as shielding, orientation, etc.) in design. To account for these effects in a directionality adjustment, the factor described above for open terrain would need to be transformed to other terrains/exposures. A "local" directionality factor, therefore, must effectively combine these two adjustments (event directionality and siting or local exposure directionality). By also considering the direction-specific aerodynamic coefficient, a direction-dependent wind load can be evaluated. While the data necessary to make predictions of directional wind loads may not routinely be available in the case of low-rise structures, the concept is discussed and illustrated in this paper.