• International Journal of Aeronautical and Space Sciences
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• 제8권1호
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• pp.115-121
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• 2007

The aeroelastic analysis of rotor blades with trailing edge flaps, focused on reducing vibration while minimizing control effort, are investigated using large deflection-type beam theory in forward flight. The rotor blade aerodynamic forces are calculated using two-dimensional quasi-steady strip theory. For the analysis of forward flight, the nonlinear periodic blade steady response is obtained by integrating the full finite element equation in time through a coupled trim procedure with a vehicle trim. The objective function, which includes vibratory hub loads and active flap control inputs, is minimized by an optimal control process. Numerical simulations are performed for the steady-state forward flight of various advance ratios. Also, numerical results of the steady blade and flap deflections, and the vibratory hub loads are presented for various advance ratios and are compared with the previously published analysis results obtained from modal analysis based on a moderate deflection-type beam theory.

• 한국항공운항학회지
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• 제8권1호
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• pp.67-81
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• 2000

An experimental study was performed on the time lag, lift and drag characteristics of a multi functional spoiler which is a device to increase lift and drag contrary to conventional spoiler which decrease lift and increase drag. In this study, a wind tunnel investigation was made of the effect of incidence angle, slot width, and chordwise location of multi functional spoiler on the time lag, lift and drag characteristics of a wing. The results indicate that the time lag of a multi functional spoiler is influenced mainly not only by the chordwise location of a spoiler but also by the slot width between spoiler and wing upper surface. Multi functional spoiler can reduce time lag effectively by slotting the trailing edge of spoiler with slot ratio (slot width devided by the wing chord length) between 0.05 and 0.1. Also, it shows that the lift and drag coefficients of the wing with the multi functional spoiler and trailing edge flap are increased by 20% and 80%, respectively, compared to the wing with trailing edge flap only.

• 항공우주산업기술동향
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• 제4권1호
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• pp.34-43
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• 2006

헬기는 비행에 필요한 추력, 모멘트 및 조종력을 회전하는 로터시스템에서 발생시키기 때문에 근본적으로 진동이 많이 생기는 항공기이다. 로터시스템의 회전에 의해 발생되는 진동소스를 제어함으로써 헬기 동체에 전달되는 진동을 감소시키고자 하는 연구들이 지금까지 수많이 진행되었다. 이러한 연구들을 크게 두 가지로 분류하면, 수동적 진동제어 방법과 능동적 진동제어 방법으로 나눌 수 있다. 수동적 진동제어 방법은 그간 오랫동안 연구되어 현재 운용 헬기에 실제적으로 적용되고 있으나 능동적 진동제어 방법은 최근까지 활발한 연구가 진행되고 있는 상태이다. 본 논문의 서론에서는 헬기 진동제어를 위한 일반적인 방법에 대한 개요를 소개하였다. 본문은 로터시스템 진동제어 기술 중 최근까지 연구가 진행되고 있는 능동적 진동제어 방법을 중심으로 기술하였다. 특히 최근 비행시험에 성공하여 거의 실용화 단계에 이르고 있는 PZT를 이용한 Trailing Edge Flap 기술, Active Twist Rotor 등을 중점적으로 소개하였다. 마지막으로 유로콥터 BK117의 ADASYS 로터 시스템 성공사례 및 향후 해결해야 할 기술적 제한사항 등을 간략하게 기술하였다.

• 한국항공우주학회지
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• 제37권12호
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• pp.1173-1183
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• 2009

스마트 무인기 익형 주위의 유동 구조를 파악하고 이를 바탕으로 synthetic jet을 이용하여 정지 비행 모드에서의 수익하중 감소 여부를 파악하였다. 스마트 무인기의 실제 비행 모드에 대하여 유동 구조를 분석하여 앞전 및 뒷전에서 발생하는 와류에 의해서 수익 하중이 크게 증가함을 밝혔다. 이에 앞전과 뒷전에서 발생하는 유동의 박리를 제어하기 위하여 0.01c, $0.3c_{flap}$, $0.95c_{flap}$ 위치에 jet을 위치시켰다. 또한 무차원 주파수(F+)의 변화에 따른 유동 구조 변화와 항력 감소율을 알아보았다. 그 결과, 와류의 유동 구조를 변화시켜 앞전과 뒷전에서 발생하는 거대한 와류의 박리 주기를 짧게 하고 와류의 크기를 감소시켜 정지 비행 모드에서 수익 하중을 효과적으로 감소시킬 수 있었다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2000년도 추계 학술대회논문집
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• pp.32-38
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• 2000

Wing flap deflection angles of a supersonic transport are optimized to improve transonic cruise performance. For this end, a numerical optimization method is adopted using a three-dimensional unstructured Euler code and a discrete adjoint code. Deflection angles of ten flaps; five for leading edge and five fur railing edge, are employed as design variables. The elliptic equation method is adopted for the interior grid modification during the design process. Interior grid sensitivities are neglected for efficiency. Also tested is the validity of the approximate gradient evaluation method for the present design problem and found that it is applicable for loading edge flap design in cases of no shock waves on the wing surface. The BFGS method is used to minimize the drag with constraints on the lift and upper surface Mach numbers. Two design examples are conducted; one is leading edge flap design, and the other is simultaneous design of leading edge and trailing edge flaps. The latter gave a smaller drag than the former by about two counts.

• Smart Structures and Systems
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• 제20권3호
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• pp.311-328
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• 2017

The characteristics of boundary layers have significant effects on the aerodynamic forces and vibration of the wind turbine blade. The incorporation of active trailing edge flaps (ATEF) into wind turbine blades has been proven as an effective control approach for alleviation of load and vibration. This paper is aimed at investigating the effects of external trailing edge flaps on the flow pattern and velocity distribution within a boundary layer of a NREL 5MW reference wind turbine, as well as designing a new type of velocity sensors for future validation measurements. An aeroelastic-aerodynamic simulation with FAST-AeroDyn code was conducted on the entire wind turbine structure and the modifications were made on turbine blade sections with ATEF. The results of aeroelastic-aerodynamic simulations were combined with the results of two-dimensional computational fluid dynamic simulations. From these, the velocity profile of the boundary layer as well as the thickness variation with time under the influence of a simplified load case was calculated for four different blade-flap combinations (without flap, with $-5^{\circ}$, $0^{\circ}$, and $+5^{\circ}$ flap). In conjunction with the computational modeling of the characteristics of boundary layers, a bio-inspired hair flow sensor was designed for sensing the boundary flow field surrounding the turbine blades, which ultimately aims to provide real time data to design the control scheme of the flap structure. The sensor element design and performance were analyzed using both theoretical model and finite element method. A prototype sensor element with desired bio-mimicry responses was fabricated and validated, which will be further refined for integration with the turbine blade structures.

• 한국항공우주학회지
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• 제40권6호
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• pp.499-505
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• 2012

회전익 항공기에서 가장 심각한 문제의 한 가지는 로터의 회전에 의한 진동 가진이다. 이를 완화하기 위하여 본 논문에서는 능동 뒷전플랩(ATF)을 적용한 로터 블레이드를 개발하였다. 이 플랩은 로터 중심에서부터 65~85% 스팬에 장착되었다. 블레이드 회전 속도는 끝단에서 마하수를 충족하기 위하여 1,528rpm정도로 높은 수준이다. 이런 특별한 장치가 내부에 삽입된 블레이드에서는 구조적인 강건성을 파악하고 관찰하는 것이 중요하다. 플랩을 작동시키는 세밀한 부품들이 회전하는 블레이드 내에 삽입되기 때문이다. 블레이드의 구조적 설계와 분석을 위하여 CAMRAD-II와 1차원 보 모델을 이용하였다. 동시에 3차원 유한요소 해석 프로그램인 MSC. PATRAN/NSTRAN를 통해 현재 블레이드의 상세한 해석을 수행하였다. 그 결과 개발한 로터의 특성이 적절한 수준인 것으로 예측되었다.

• 대한기계학회논문집 C: 기술과 교육
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• 제2권1호
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• pp.39-46
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• 2014

이 연구에서는 탄성 플랩이 뒷전에 장착된 2차원 날개 단면의 공력 특성을 전산 해석하였다. EDISON_CFD는 날개 주위의 비압축성 난류 유동을 시뮬레이션 하기 위해 이용되었으며, MIDAS_IT는 전산 해석 결과로 얻어진 압력 하중 하에서 탄성 플랩의 변위를 구조해석 하기 위해 사용되었다. EDISON_CFD와 MIDAS_IT의 반복 계산 절차를 이용하여, 플랩의 변위가 수렴되면 해석을 종료하여, 날개 단면에 작용하는 공력을 분석하였다. 양항비의 추정 결과 일정 받음각 이내에서 플랩의 유리한 효과가 나타날 것으로 예상된다.

• International Journal of Aeronautical and Space Sciences
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• 제13권1호
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• pp.58-63
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• 2012

In general, a conventional flap on an aircraft wing can reduce the aerodynamic efficiency due to geometric discontinuity. On the other hand, the aerodynamic performance can be improved by using a shape-morphing wing instead of a separate flap. In this research, a new flap morphing mechanism that can change the wing shape smoothly was devised to prevent aerodynamic losses. Moreover, a prototype wing was fabricated to demonstrate the morphing mechanism. A shape memory alloy (SMA) wire actuator was used for the morphing wing. The specific current range was measured to control the SMA actuator. The deflection angles at the trailing edge were also measured while various currents were applied to the SMA actuator. The trailing edge of the wing changed smoothly when the current was applied. Moreover, the deflection angle also increased as the current increased. The maximum frequency level was around 0.1 Hz. The aerodynamic performance of the deformed airfoil by the SMA wire was analyzed by using the commercial program GAMBIT and FLUENT. The results were compared with the results of an undeformed wing. It was demonstrated that the morphing mechanism changes the wing shape smoothly without the extension of the wing skin.

• International Journal of Fluid Machinery and Systems
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• 제1권1호
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• pp.109-120
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• 2008

An innovative method of changing a centrifugal low specific speed pump performance and pressure fluctuation by applying outlet flaps to impeller exit has been investigated. The outlet blade edge section corresponds to the trailing edge of wing on the circular-cascade, which dominates the pump performance and pressure fluctuation. Computational fluid dynamics (CFD) analysis of the entire impeller and volute casing and an experimental investigation are conducted. The pressure fluctuation and the vibration of the shaft are measured simultaneously. Kurtosis is applied as a dimensionless parameter with which the unevenness of velocity distribution at impeller outlet is indicated. The influence of the flaps on the pressure fluctuation is explained by the kurtosis. This paper presents a theoretical method of predicting the pump performance related to the attachment of a flap at impeller outlet.