• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.8
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• pp.758-766
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• 2010

The design procedure of Solar Power UAVs is complicated because the configuration and required power for flight must be considered simultaneously as the supplied power is influenced by the wing area. In order to minimize trial and error for the Solar Power UAVs design, a systematic sizing method is proposed which can be used to determine whether a Solar Power UAV is feasible for a given mission, and to derive preliminary dimensional specification of it. The sizing procedure begins with initially assumed wing area because the power, lift, and drag of the wing are directly proportional to it. The assumed wing area and mission requirements are then used to determine step by step the airfoil specifications including lift coefficient and drag coefficient, weight, required power, and wing area. This procedure is iterated for each newly assumed wing area until the error between the assumed wing area and calculated wing area becomes significantly small enough. This sizing methodology was applied to previously developed Solar Power UAVs for validation purposes, resulting in good agreement. The methodology was also applied to determine the dimensions and specifications of the Solar Power High-Altitude Long-Endurance UAV.

• Journal of the Korea Convergence Society
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• v.12 no.2
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• pp.215-219
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• 2021

The flow analyses around the wing of airplane installed with winglet or sharkelt were carried out in this study. At the model without winglet, it can be seen that the air flows beside the wing and the flow is concentrated at the end of wing. At the model of winglet or sharklet, the pressure on the bottom of the wing happens to be lower in the wide area than for model without winglet. At the analysis result, the air flowing next to the wing can be seen to go over and rotates over the main wing. The model with the sharklet shows that the flow rate is the fastest. In case of model with sharklet, it is thought that the maximum total pressure of flow is distributed at the bottom of the wing, which can further improve the lift force of the wing. It is thought that the analysis results in this study on the air flow due to the configuration of aircraft edge wing can be helped at its convergent research.

• Proceedings of the KIPE Conference
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• 2017.11a
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• pp.81-82
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• 2017

기존의 배풍기 효율을 높이기 위해서 모터와 제어방식 그리고 임펠러 형상에 변화를 주는 시스템 설계에 관한 연구다. 본 논문에서는 임펠러 속도는 5500rpm으로 증가시키고 크기는 320mm에서 250mm로 줄였으며 효율과 최대 풍량을 향상키기기 위해 임펠러의 Hub/Tip 비율을 줄이며, 날개각도에 변화를 주는 방식을 제안한다. 여기서 Hub/Tip 비율이 줄어들면 임펠러 날개의 면적이 늘어나 유량이 증가하게 되고, 임펠러 중심 거리에 따른 날개 각도를 변화시키면 배풍기 속도에 대한 풍압과 풍량이 달라져 배풍기의 효율을 높일 수 있다. 설계된 구동용 SRM과 임펠러의 설계에 따른 운전 특성을 시뮬레이션을 통해 해석하고자 한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.7
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• pp.575-580
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• 2007

During the conceptual design phase of a canard type high maneuverable aircraft, the low speed small scale wind tunnel test was conducted to investigate the high angle-of-attack static stability of the aircraft. In this study, 1/50th scale generic canard-body-wing model was used for the small scale wind tunnel test. For the analysis of static stability including high angle-of-attack nonlinear characteristics, the vertical tail effects were studied due to canard deflections. In addition, the nose chine effects were studied at high angle-of-attack. Based on the results obtained from the experimental study, the configuration change effects for canard type aircraft on high angle-of-attack static stability have been able to analyze.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.1
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• pp.162-174
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• 1992

Blades are one of the critical parts of the wind machine. This paper presents a design procedure for the blade of a 7m diameter horizontal axis wind turbine with the constraint conditions of stresses and fundamental frequency. This blade consists of glass/polyester woven fabric and unidirectional prepreg. It was firstly designed by the classical beam theory on the assumption that torque box sustains all external loads and the reliability of the blade was then inspected in the preliminary estimation by using FEM.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.6
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• pp.468-476
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• 2016

In this study, the conic winglet which is made by rotating wing tip airfoil by each 3 axis is applied to the dual type combined fan to reduce the wing tip leakage loss. Computational Fluid Dynamics is used to calculate the loss and optimum technique is used to get minimum loss. Optimization results shows that total pressure loss coefficient was reduced by 3.4 %, and optimization model was a bended shape at the end of wing forward to pressure side.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.3
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• pp.29-37
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• 2000

Because the previous design procedure for the composite wind turbine blade structure using trial and error method takes long time, a improved design procedure by using the program based on classical laminate theory was proposed to reduce the inefficient element. According to the improved design procedure, limitation of strains, stresses and displacements specified by international standard specification IEC1400-1 for the composite wind turbine blade were applied to sizing the structural configuration by using the rule of mixture and the principal stress design technique with a simplified turbine blade. Structural safety for strength and buckling stability was confirmed by the developed analysis program based on the laminate theory to minimize the design procedure. After modifying the preliminary design result with additional structural components such as skin, foam sandwich and mounting joints, stresses, strains, displacements, natural frequency, buckling load and fatigue life were analyzed by the finite element method. Finally these results were confirmed by comparing with IEC1400-1 specification.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.10
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• pp.846-852
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• 2012

The present paper is the preliminary study of the development of a morphing aircraft wing and investigates experimently the aerodynamic characteristics of a base airfoil and a morphing airfoil. The wind tunnel tests are conducted for a base Clark-Y airfoil, an airfoil with a mechanical flap, and a morphing airfoil. Lifts, drags, and pitching moments are measured by using a three-axis load cell and they are calibrated by considering solid blockage and wake blockage. The wind tunnel tests are conducted for various air speeds, Reynolds' numbers, and angles of attack. The experimental results show that the aerodynamic characteristics of the morphing airfoil in lift-drag and lift-pitching moment are better than those of the airfoil with a mechanical flap.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.4
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• pp.8-15
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• 2003

A practical design method for supersonic wings has been developed. The method is based on Takanashi's method that uses integral equations and iterative "residual-correction" concept. The geometry correction is calculated by solving linearized small perturbation equation (LSP) with the difference between garget and objective surface pressure distributions as a boundary condition. In the present method, LSP equation is analytically transformed to integral equations by using the Green's theorem. Design results of an isolated wing and wing-nacelle configurations are presented here.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.90-90
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• 2011

배기속도 2,500 L/s, 최고진공도 10-10 mbar를 구현할 대용량 복합 분자펌프 설계를 위한 2차원과 3차원 형상을 대상으로 실시하였다. 진공도가 10-5 mbar 이상이 되는 고진공도에서는 Knudsen 수가 102~107에 이르러 분자간 충돌을 거의 무시할 수 있게 되며, 이때의 유체해석 방법으로서는 통상 희박기체 해석법으로 많이 쓰이는 Direct Simulation Monte Carlo (DSMC) 방법보다, 충돌이 없는 분자의 자유운동을 모사하는 Monte Carlo 방법이 더 적합하게 된다. 본 연구에서는 다단계 rotor와 stator로 구성되는 복합분자 내 유동장에 Monte Carlo 해석법과 DSMC 방법을 모두 적용하여 유동해석을 실시하였다. 먼저 2차원 모델에 대한 해석을 실시하여 분자펌프의 성능에 중요한 영향을 미치는 설계변수로 날개각과 날개간격이 현저함을 확인하였으며, 이 설계변수들이 펌프의 주요성능 지표인 최대펌핑효율과 최대압축비에 미치는 영향을 다양한 3차원 유동해석을 통해 도출하였다. 유동해석 결과, 기체분자와 rotor 날개사이의 충돌 확률을 높이는 방안이 대체적으로 펌프의 성능을 향상시키는데 도움이 되는 것으로 나타났다.