• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.202-205
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• 2011

A rotating propeller of turboprop aircraft gives much effect on the aerodynamic characteristics of wing such as lift, moment and stall. Specially, a rotating propeller changes the lift and moment characteristics when aircrafts are in landing or take-off condition. In the present paper, 3-dimensional Navier-Stokes simulations for the interaction of propeller and wing were carried out. For rotating propeller, unsteady sliding mesh method was used to simulate a relative motion. For the power effect analysis in landing and take off configurations, double slotted flap was also considered and the aerodynamic characteristics were investigated. It was shown that the propeller slipstream enhanced the lift slope including maximum lift and this enhancement was more dominant with high lift device.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.631-638
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• 2003

The wind turbine blade is the equipment converted wind into electric energy. The effect of the blade has influence of the output power and efficiency of wind turbine. The design of blade is considered of lift-to-drag ratio, structure, a condition of process of manufacture and stable maximum lift coefficient, etc. This study is used the simplified method for design of the aerodynamic blade and aerodynamic analysis used blade element method. This process is programed by delphi-language. The program has any input values such as tip speed ratio, blade length, hub length, a section of shape and max lift-to-drag ratio. The program displays chord length and twist angle by input value and analyzes performance of the blade.

• Journal of Electrical Engineering and Technology
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• 제9권5호
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• pp.1712-1718
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• 2014

Experimental analysis according to the plasma actuator design variables was performed in order to verify the effects of sliding discharge plasma on aerodynamic drag reduction of a high-speed train. For the study, sliding discharge plasma actuator and high-frequency, high-voltage power supply were developed and experimented to figure out the best design variables for highest ionic wind velocity which could reduce the drag force. And then, 5% reduced-scale model of a high-speed train was built for wind tunnel test to verify it. From the results, it was confirmed that sliding discharge plasma had contribution to reduce the drag force and it had the potential to be applied to real-scale trains.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.1207-1214
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• 2001

The paper deals with the computational approach in analysis and design of pantograph panhead strips of high-speed railway in aerodynamic and aeroacoustic concerns. Pantograph is an equipment such that the electric power is supplied from catenary system to train. Due to the nature of complexity in high-speed fluid flow, turbulence and downstream vortices result in the instability in the aerodynamic contact between panhead strips and catenary system, and consequently generate the considerable levels of flow-induced sound. In this paper, based on the preceding low speed wind-tunnel test and simulations, the aerodynamic and aeroacoustic characteristics in low speed are analyzed.

• Structural Engineering and Mechanics
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• 제20권4호
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• pp.435-450
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• 2005

Here, the dynamic instability characteristics of aero-thermo-mechanically stressed functionally graded plates are investigated using finite element procedure. Temperature field is assumed to be a uniform distribution over the plate surface and varied in thickness direction only. Material properties are assumed to be temperature dependent and graded in the thickness direction according to simple power law distribution. For the numerical illustrations, silicon nitride/stainless steel is considered as functionally graded material. The aerodynamic pressure is evaluated based on first-order high Mach number approximation to the linear potential flow theory. The boundaries of the instability region are obtained using the principle of Bolotin's method and are conveniently represented in the non-dimensional excitation frequency-load amplitude plane. The variation dynamic instability width is highlighted considering various parameters such as gradient index, temperature, aerodynamic and mechanical loads, thickness and aspect ratios, and boundary condition.

• 동력기계공학회지
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• 제10권2호
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• pp.22-28
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• 2006

Computer simulation of the air flow over an automotive vehicle is now becoming a routine process in automotive industry to assess the aerodynamic characteristics of a medium-size vehicle such as $C_d\;and\;C_1$ and aslo to investigate the possibility of improving aerodynamic performance of the vehicle as a preliminary design for the production line. Mainly due to its contribution in saving time and cost in the development of new cars, computer simulation of the air flow over a vehicle is usually done well before a production car is introduced to the market and in gaining more and more attention as powerful computer resources are getting readily available nowadays. To aerodynamically design a car is mainly related with reducing a drag coefficient of car. A well designed car usually has a $C_d$ value in the range of $0.3{\sim}0.4$. It is understandable that automotive industry is rushing to reduce a drag coefficient as reducing even a small fraction of the $C_d$ value can have an enormous overall impact on many areas. Actually, the present research model was able to achieve a $C_d$ value in the range of $0.3{\sim}0.36$ for flow velocities of $60km/h{\sim}100km/h$ by strategically removing the possible factor hazardous to lower $C_d$ value. Prediction of the medium-size vehicle aerodynamics using CFD was performed when an actual car model was in the development stage and three-dimensional modeling was also performed to optimize it as the best model in terms of the best aerodynamic performance.

• 한국항공우주학회지
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• 제35권10호
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• pp.891-898
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• 2007

피치 제어형 수평축 풍력터빈에 대한 공력최적 설계 형상과 피치 변화에 따른 공력 성능 특성을 수치적으로 계산하였다. 수치적 방법은 날개 요소이론을 적용하였으며, Prandtl의 팁 손실 효과, 에어포일의 분포 효과, 후류의 회전 효과 등을 고려하였다. 블레이드 설계에는 총 6개의 서로 다른 에어포일을 사용하였으며, 구조적 강성을 갖기 위해서 허브 측에는 최대 40% 두께비의 에어포일을 분포시켰다. 최적 설계에서 얻어진 비선형 코드 길이는 제작성과 무게 등을 고려하여 선형화 시켰고, 선형화에 따른 공력성능 변화는 무시할만하다는 결과를 얻어내었다. 피치각 변화에 따른 동력성능, 추력성능, 토크 성능 곡선을 비교한 결과 $3^{\circ}$의 피치각 변화에도 민감한 공력 값의 변동이 생김을 알 수 있었고, 정밀한 피치 제어를 위한 각도 제어는 증분이 $3^{\circ}$보다 작은 값으로 피치 제어 알고리즘과 피치 구동 장치가 필요함을 알 수 있었다. 또한 최대 토크는 설계속도비보다 작은 속도비에서 발생되는 결과를 보여주었다.

• 한국항공우주학회지
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• 제44권5호
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• pp.391-398
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• 2016

본 연구에서는 난류 유입조건을 갖는 수평축 풍력터빈 블레이드의 공력 하중에 대해 초점을 맞추어 연구하였다. 난류모델은 풍속과 방향에 대한 변동을 포함하며, 그 특성은 난류 강도와 표준편차로 표현된다. IEC61400-1에서는 정상 난류 모델과 정상 풍속 측면도에 대해서 피로해석을 수행하도록 규정하고 있다. 이를 위해 공력 최적설계 절차를 통해 얻어낸 MW급 수평축 풍력터빈 블레이드 허브와 저속 회전축에 대한 공력하중 해석을 수행한다. 공력하중 성분은 수치적인 절차를 통해 얻어내며 이를 블레이드 회전 특성을 고려하여 해석적으로 검토하였다. 난류 조건을 고려했을 때의 최대 추력과 토크의 변동치는 난류 조건을 고려하지 않았을 때의 값들에 비해 5~8 배 더 큰 값을 보였다. 따라서 난류 조건을 반영한 하중 해석은 풍력터빈 블레이드의 구조설계에 있어서 필수적임을 확인하였다.

• 한국농공학회논문집
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• 제63권5호
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• pp.63-71
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• 2021

Windbreak forests, which have a windproof effect against strong winds, are known to be effective in reducing the spread of odors and dust emitted from livestock farms. The effect of reducing the spread of odors and dust can be estimated through numerical models such as computational fluid dynamics, which require aerodynamic coefficients of the windbreaks for accurate prediction of their performance. In this study, we aimed to evaluate the aerodynamic coefficients, Co, C₁, C₂, and α, of two windbreaks, Thuja occidentalis and a mesh net, through wind tunnel experiments. The aerodynamic coefficients were derived by the relation between the incoming wind speed and the pressure loss due to the windbreaks which was measured by differential pressure sensors. In order to estimate the change in the aerodynamic coefficient concerning various leaf density, the experiments were conducted repeatedly by removing the leaves gradually in various stages. The results showed that the power law regression model more suitable for coefficient evaluation compared to the Darcy-Forchheimer model.

• 대한토목학회논문집
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• 제30권1A호
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• pp.27-33
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• 2010

본 연구에서는 소형 풍력발전기를 교량에 설치하여 전력생산과 아울러 내풍안정성을 개선할 수 있는 방안을 연구하였다. 이를 위하여 기존 공기역학적 진동억제 대책과 유사하게 교량에 풍력발전기를 설치하기 위한 방법과 풍력에너지 추정 방법을 제시하였다. 풍동실험 결과를 보면, 페어링처럼 소형 풍력발전기를 설치하면 와류진동을 거의 억제할 수 있는 것으로 나타났고, 이때 교축방향 최적 이격 거리는 터빈 직경의 3-4.5배인 것으로 나타났다. 그리고 풍력발전기를 설치하면 항력계수는 낮아지고 양력계수의 기울기도 음에서 양의 값으로 바뀌어 전반적인 내풍안정성이 향상되는 것으로 나타났다. 한편 풍하측의 풍력발전기는 평균풍속이 낮아 발전을 못하지만, 풍상측의 풍력발전기는 상당량의 전기에너지를 생산하는 것으로 나타났다.