• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.41 no.4
• /
• pp.268-274
• /
• 2013

In this paper, objective functions are defined for optimization of radar absorbing structures (RAS) on the aircraft wing leading edge. RAS is regarded as a single layer structure made of dielectrics. Design variables are the real and imaginary parts of complex permittivity. Reflection coefficient(RC) and radar cross section(RCS) are used in the objective function respectively. Transmission line theory is employed to calculate the RC. The RCS is evaluated by using physical optics(PO) for a leading edge part model. Genetic algorithm(GA) is used to perform optimization procedures. The radar absorbing performance of designed RAS is assessed by the RCS of a wing which has RAS on the leading edge.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1992.10a
• /
• pp.330-334
• /
• 1992

현재 제품의 보다 향상된 의장성과 기능성을 위해서 정밀한 자유곡면 형상의 제품에 대한 수요가 증가함에 따라 자유곡면 형상 제품의 효율적이고 정밀한 설계 및 가공과 함께 제품에 대한 수치 검사가 더욱 중요해지고 있다. 이러한 자유곡면 형상 제품의 예로는 금형, 헬리콥터 프로펠러, 비행기 날개 등이 있다. 이러한 제품의 설계 및 가공을 위해서 많은 CAD/CAM 시스템이 개발되었다. 수치 검사 분야에서는 기하학적으로 복잡한 제품에 대한 정밀하고 효율적인 검사를 위해서, 3차원 좌표측정기을 포함한 컴퓨터의 구동의 수치 검사 장비가 개발되고, 그러한 장비를 이용한 CAI 시스템사용이 다양한 분야에서 점차 증가하고 있다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 1997.11a
• /
• pp.22-22
• /
• 1997

무공해 에너지원은 화석에너지의 고갈과 환경오염의 심각한 문제로 인하여 절실히 요구되고 있는 실정이다. 그중 풍력발전 시스템은 타 에너지원에 비해 여러 가지 측면에서 유리한 점을 가치고 있다. 본 연구에서는 500Kw급 풍력발전 시스템을 개발함에 있어, 적합한 공력 성능 및 구조성능을 가지는 회전날개 설계과정을 수행하였다. 공력설계는 운용지역의 풍황을 고려하여 회전날개의 외형을 결정하였고 이를 바탕으로 공력성능해석이 수행되었으며, 구조설계는 복합재료를 사용하여 쉘-스파 구조를 갖도록 설계하여 굽힘 및 비틀림 그리고 피로수명에 대한 구조해석이 수행되었다. 그 결과 4m/s의 미풍에서도 운용가능하며, 12m/s에서는 정격출력 550Kw를 생산할 수 있는 형상이 설계되었고, 또한 20년 이상의 피로수명이 확보되었으며, 공질 등의 동적인 문제도 발생하지 않음을 확인하였다.

• Proceedings of the KSME Conference
• /
• 2001.06e
• /
• pp.588-594
• /
• 2001

본 연구를 통해 초음속 전투기 날개의 공력-구조를 동시에 고려한 다학제간 설계를 수행하였다. 공력해석을 위해 사용된 3 차원 Euler Code는 수렴 속도를 개선하기 위해 Multigrid를 적용하였으며, 3차의 transfinite interpolation을 사용하여 O-H type의 공력해석 격자계를 생성하였다. 구조 분야는 절점당 54개의 자유도를 가지는 9 절점 쉘 혼합 유한요소(9-node shell mixed finite element)를 사용하여 해석을 수행하였다. 설계변수는 공력쪽으로 날개의 평면형상에 관련된 변수 3개, 구조쪽은 날개 윗면과 아래면의 표피두께에 관련된 4개의 설계변수 사용하였으며, D-optimality 조건을 만족시키는 실험점들에 대해 공력해석과 구조해석이 연동된 정적 공탄성 해석을 수행한 후, 반응면 기법을 이용하여 목적함수와 제약조건에 대한 반응면을 구성하였다. 단일점 설계를 수행한 후 이를 바탕으로 3개의 설계점을 동시에 고려한 다점 설계를 수행하였으며, 공력만을 고려한 설계 결과와 공력-구조를 동시에 고려한 다학제간 설계결과의 비교를 통해 다학제간 설계의 타당성과 우수성을 입증하였다.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.31 no.3A
• /
• pp.145-152
• /
• 2011

Current Bridge Specification for Highway Bridges adopts a simplified method to determine sectional forces of abutment wing by dividing its area into four sections. This simplified method was developed in Japan when numerical analysis was not mature and computer resources were expensive. This simplified method has been with us without modification. This study evaluates the problem of current design practice to improve the design guideline for abutment wing. In this study, a finite element model of abutment wing based on shell elements was developed to obtain accurate sectional force. In addition, foreign design specifications regarding abutment wing were thoroughly examined. It has been observed that sectional forces obtained from the simplified method produce inaccurate results under various geometric shapes. Thus, it is recommended that two dimensional plate analyses should be adopted for future design of abutment wing wall.

• Journal of the Korea Convergence Society
• /
• v.5 no.4
• /
• pp.75-79
• /
• 2014

In this study, a flow analysis is carried out on the wing shape of cooling fan at automobile. By designing three kinds of Canival, Teracan and basic models with CATIA program, this analysis is done on the configuration of cooling fan with the same flow condition. It can be seen that the contour of flow velocity is changed due to the model of wing and the pressure distribution of fluid is changed due to the configuration or the area of wing. In case of cooling model of Teracan among three models, there is the most air flow and it can be thought to be most effective to cool the radiator. And it is possible to be grafted onto the convergence technique at design and show the esthetic sense.

• Proceedings of the Korean Nuclear Society Conference
• /
• 2004.05a
• /
• pp.113-113
• /
• 2004

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.39 no.8
• /
• pp.661-668
• /
• 2015

We present a design methodology for horizontal-axis tidal turbine blades based on blade element momentum theory, which has been used for aerodynamic design and power-performance analysis in the wind-energy industry. We design a 2-blade-type 1 MW HATT blade, which consists of a single airfoil (S814), and we present the detailed design parameters in this paper. Tidal turbine blades can experience cavitation problems at the blade-tip region, and this should be seriously considered during the early design stage. We perform computational fluid dynamics (CFD) simulations considering the cavitation model to predict the power performance and to investigate the flow characteristics of the blade. The maximum power coefficient is shown to be about 47 under the condition where TSR = 7, and we observed cavitation on the suction and pressure sides of the blade.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.44 no.7
• /
• pp.562-567
• /
• 2016

Morphing wing which has a configuration optimized to flight speed and condition is faced to a lot of barriers to be overcome such as actuator technique, structural mechanization technique, flexible skin material, control law, and so on. As the first step for developing a morphing wing with rapid response, we designed and fabricated the morphing airfoil using a SMA(shape memory alloy) wire actuator and torsional bias springs. The design concept of the morphing airfoil was verified through operation test. The measured results show that the flap deflects smoothly and fast.

• Journal of Aerospace System Engineering
• /
• v.15 no.1
• /
• pp.40-46
• /
• 2021

In this study, an aerodynamic configuration design and study on performance enhancement of a tilt-rotor UAV were conducted for improving mission capabilities compared to multi-copter type UAV, MC-1/2/3 developed for disaster and policing operation. To improve performance, a new TR5X configuration was developed by modifying the fuselage and tail shape of TR60 UAV and additionally attaching an extended wing to the nacelle. Aerodynamic performances of TR60 and TR5X were compared through computational fluid dynamics (CFD) analysis. In addition, flight performance analysis of full aircraft was conducted. Results showed that main performance requirements of TR5X were satisfied.