• Journal of the Society of Naval Architects of Korea
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• v.50 no.1
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• pp.25-32
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• 2013

The shape of a conventional full spade rudder has been modified to implement the Coanda effect and consequential changes in the flow characteristics are carefully examined to show the significant enhancement in the lift performance. A preliminary numerical study has been done to identify the optimum configuration of the modified rudder sections. For the purpose, chord wise locations of the jet slit and the radii of the trailing edge were varied in several ways and the changes in the lift characteristics have been observed at the various angles of attack, particularly focusing on the usefulness of the Coanda effect upon delaying the stall or increase in the circulation. Making the most use of the results so attained, full spade rudder of a VLCC has been reformed to realize the Coanda effect. A series of model experiments and numerical simulations are performed to confirm the effectiveness of the Coanda effect in improving the performance of the modified rudder. It is found that considerable enhancement in the lift performance of the rudder is plausible at any rudder angle if an optimum jet momentum is provided.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.2
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• pp.57-80
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• 1994

항공기에 사용되는 2차 조종면은 플랩, 탭, 스포일러 등 여러 종류가 있으며 이중 spoiler는 공력제어 기능을 가지고 항공기의 조종성에 영향을 미치는 조종면으로 속도 감속이나 옆놀이 조종용으로 사용된다. 본 연구에서는 비행제어용 spoiler 기능과 고양항력을 얻을 수 있는 새로운 장치인 고양항력 panel에 대한 공력특성 및 비행제어 특성에 대하여 연구하였다. 이러한 고양항력 panel은 재래식인 spoiler가 양력을 감소시키고 항력만 증가시키는 장치인데 반하여 양력과 항력을 동시에 증가 시킬 수 있는 새로운 장치로서 날개의 앞전 윗면에 스팬방향으로 설치하여 슬롯효과를 발생시킴으로써 최대 양력 받음각에서 앞전에서의 박리를 막아 비행기의 착륙시 양력의 급작스러운 감소로 인한 불안정성을 감소시키게 된다. 본 논문에서는 직사각형 날개 및 FA-200모형의 날개위에 고양항력 panel을 설치하여 풍동실험 및 수치계산을 한 결과를 기술하였다. 실험결과 직사각형 날개의 경우 고양항력 panel의 위치는 날개의 앞전에 설치할 경우 고받음각에서 실속지연의 효과와 함께 후방실속의 특성을 향상 시킬 수 있으며, 항력의 증가로 인한 스포일러 효과를 얻을 수 있다. 양항비특성은 고양항력 panel을 날개의 앞전에설치하고, 그폭이 시위의 1/5이고, 붙임각 ${\theta}$가 $10^{\circ}$, 높이가 시위의 3/20일때 받음각 $18^{\circ}$ 이후에서 우수한 특성을 나타내었다. FA-200 모형의 경우 옆놀이 모멘트계수는 받음각이 작을 때 고양항력 panel의 슬롯간격과 붙임각이 작을수록 커지나 받음각이 커지면 붙임각이 커짐에 따라 증가함을 알 수 있다. 또한 키놀이 모멘트계수는 크게 변화하지 않으나 항력 특성은 고양항력 panel의 붙임각이 증가함에 따라 증가하였다. 고양항력 panel의 붙임각이 큰 범위에서 (${\theta}$ =$10^{\circ}$) 공기력의 증가는 고양항력 panel의 시위가 날개시위의 30%이고 슬롯의 폭이 날개시위의 10%일때 증가하는 결과를 얻을 수 있다.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.2
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• pp.188-197
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• 2007

Active flow control, in the form of steady and unsteady momentum injection via jet blowing was studied. A jet was obtained by pressing a plenum inside the airfoil and ejecting flow out of a thin slot. The normal and drag forces were measured with leading edge or trailing edge blowing Jet and compared with the results obtained with no blowing. The blowing jet has been shown to improve the aerodynamic performance of the airfoil. The steady jet proved more effective than pulsating jet in these experimental conditions. Furthermore for the case of leading edge steady blowing jet, the alleviation of non-linearity in the normal force curve slope can be seen at higher angles of attack. No effective trailing edge jet was observed in this highly separated flow. This shows that the stall control is highly depends on the characteristics of the boundary layer near the jet slot.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.744-750
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• 2001

In now a days, the concern to environment and energy saving problem is increased worldly. So many countries are developing the wind power system as clean energy system. In our country, Cheju local government has the plan of the Cheju Island wind farm and 600kW class 2 wind turbines, 660kW class 2 turbines, 225kW class 1 turbine and 750kW class 2 turbines has been operated at Hangwon. In this paper the field operation data of the wind turbines was analyzed and was compared with the characteristics & performance of each turbines. As the results, we would find the possibility of wind turbine in domestic and suggest the direction of developing technology.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.199-202
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• 1996

In this paper, we used the maximum likelihood method for 2-point aerodynamic model to determine the parameters of the ChangGong-91. Since the estimation from the flight test of real aircraft is the most reliable, we performed the flight test of ChangGong-91 to get the parameters such as velocity, height, 3 axis acceleration, 3 axis angular rate, pitch angle, angle of attack, temperature and so on. We recorded the flight test data in S-VHS tapes and stored them to personal computer using A/D(analog to digital) converter. Flight test was done in stall motion, and the acquired data was be processed with parameter identification method.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.04a
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• pp.6-6
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• 1998

중형항공기용 터보팬 엔진의 정상상태 및 천이상태 성능을 해석하고 제어기 설계를 위한 선형모델을 구하였다. 정상상태 성능해석은 설계점으로 선정한 지상정지조건과 최대상승조건(Mach=0.78, 고도=36000ft) 및 순항조건(Mach=0.78, 고도=39000ft)을 고려하였으며, 저압압축기의 공회전 상태에서 최대 회전속도까지의 부분부하성능해석을 수행하였다. 부분부하 성능해석 결과 90% RPM 조건에서 가장 연료소모율이 적어 경제적임을 알 수 있다. 동적 성능모사는 각각의 대기조건에서 연료가 Step 증가, Ramp 증가 및 감소, Step 증가 후 Ramp 감소하는 경우에 대해 수행하였다. 모사결과 고려된 모든 조건에서 연료의 Step 증가시 고압압축기의 터빈입구온도가 제한온도를 초과하여, 보다 빠른 가속과 최적의 성능을 위해서는 적절한 제어가 필요함을 알 수 있었다. 또한 최대상승조건에서 연료를 Step 증가시킬 경우 고압압축기에서 실속이 발생하여 이에 대한 대책도 필요함을 알 수 있었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.9
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• pp.729-738
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• 2021

Feedback flow control using an artificial neural network was numerically investigated for NACA0015 Airfoil to suppress flow separation on an airfoil. In order to achieve goal of flow control which is aimed to reduce the size of separation on the airfoil, Blowing&Suction actuator was implemented near the separation point. In the system modeling step, the proper orthogonal decomposition was applied to the pressure field. Then, some POD modes that are necessary for flow control are extracted to analyze the unsteady characteristics. NARX neural network based on decomposed modes are trained to represent the flow dynamics and finally operated in the feedback control loop. Predicted control signal was numerically applied on CFD simulation so that control effect was analyzed through comparing the characteristic of aerodynamic force and spatial modes depending on the presence of the control. The feedback control showed effectiveness in pressure drag reduction up to 29%. Numerical results confirm that the effect is due to dramatic pressure recovery around the trailing edge of the airfoil.

• 한국전산유체공학회:학술대회논문집
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• 2000.10a
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• pp.176-182
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• 2000

This paper presents methods for dynamic stall control utilizing an optimization approach. Unsteady aerodynamic sensitivity code is developed using a direct diffentiation method from a discrete two-dimensional unsteady compressible Navier-Stokes code including a two-equation turbulence model. Dynamic stall control is conducted by minimizing an objective function defined at an instant instead of integrating a response for a period of time. Unsteady sensitivity derivative of the objective function is calculated by the sensitivity code, and optimization is conducted using a linear line search method at every physical time level. Examples of dynamic stall control utilizing airfoils nose radius or maximum thickness variation show very satisfactory results.

• Proceedings of the KAIS Fall Conference
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• 2007.05a
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• pp.158-161
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• 2007

본 연구는 고속으로 회전하는 축류압축기(송풍기)의 설계 및 운전에 기초가 되는 축류회전 익렬에서의 유동계산과 유동측정, 그리고 고속회전에 따른 진통해석과 안전진단을 위한 이상 진단 시스템개발에 관해 연구한 것이다. 따라서 회전날개의 진통해석, 선회실속시의 회전날개의 진통해석, 전 체계의 동력학적 해석, 그리고 회전축의 비틀림 진동 및 선회진동의 제어로 나누어 수행하였다. 또한 각각의 연구에 대하여 수치해석과 실험을 병행하여 이론해석과 설정한 모델의 타당성을 검증하였다.

• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.197-206
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• 2009

To improve the aerodynamic efficiency of Smart Unmanned Aerial Vehicle (SUAV), vortex generators and flow fence are applied on the surface and the tip of wing. The initially applied vortex generator increased maximum lift coefficient and delayed the stall angle while it produced excessive increase in drag coefficient. It turns out reduction of the airplane's the lift/drag ratio. The new vortex generators with L-shape and two different height, 3mm and 5mm, were used to TR-S4 configuration to maintain the desired level of maximum lift coefficient and drag coefficient. Flow fence was also applied at the end of both wing tip to reduce the interaction between nacelle and wing when nacelle tilting angles are large enough and produce flow separation. To examine the effect of flow fence, flow visualization and force and moment measurements were done. The variation of the aerodynamic characteristics of SUAV after applying flow control devices are summarized.