• 한국운동역학회지
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• 제13권3호
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• pp.133-149
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• 2003

The purposes of present study were to determine the major check-points of golf swing from the review of previous studies, and to suggest additional information on the teaching theory of golf. The golf swing motion of 6 male and female elite university golf players were filmed with 16mm Locam II high speed cameras at the speed of 200f/s, and variables such as time, displacement, angle, velocity were calculated and analyzed by 3D Cinematography using DLT method. The results were: 1. Differences were shown in the ratio of weight distribution on the feet, cocking angle, take-back velocity, club-head velocity at impact depending upon the physical characteristics and club used for swing. 2. Time for the down-swing and impact were $0.27{\sim}0.29s$ in men and $0.29{\sim}0.32s$ in women, which was 1/3 of the time for the back-swing. Women showed longer total swing time than men because of longer time in back-swing, follow-through and finish. 3. Men showed larger range of motion in shoulder and knee joints than women, on the other hand women showed larger range of motion in hip joint than men. 4. Cocking motion and right elbow flexion were occurred at the top of back-swing and cocking release was occurred at the moment of impact. Maximum rotations of shoulder and hip joints were found between the top of back-swing and down-swing phase. 5. Women showed lower back-swing velocity than men, and men showed higher club velocity(men: $38.2{\sim}38.6m/s$, women: $35.1{\sim}36.4m/s$) than women.

• 한국항공우주학회지
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• 제46권9호
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• pp.712-722
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• 2018

본 논문에서는 곤충 모방 날갯짓 비행체의 가장 중요한 설계 변수 중 하나인 날개에 대한 파라메트릭 연구에 대해 서술하였다. 추력, 피칭모멘트, 소비전력, 추력 대 전력비의 비교 및 분석을 통해 날개 형상에 대한 실험적 연구를 진행하였다. 힘과 모멘트는 2축 밸런스를 이용하여 측정되었으며 날갯짓 주파수는 홀센서를 이용하여 측정되었다. 날개 형태는 겹 날개 형태를 채택하였으며 이를 통해 Clap and fling 효과를 구현하였다. 기준 날개 형상으로 잠자리의 날개를 선정하였고, 이를 기준으로 가로세로비 및 면적에 대한 실험을 진행하였다. 결과적으로, 가로세로비와 면적이 증가할수록 추력, 피칭모멘트, 소비전력이 증가하는 것을 확인하였다. 또한, 일정 수준 이상의 가로세로비 혹은 면적을 가지는 날개를 메커니즘에 적용하였을 때 메커니즘이 정상적으로 구동되지 않는 것을 확인하였다. 최종적으로 날개 형상 선정은 필요한 최소추력을 만족시키는 날개 중에서 추력 대 전력비를 비교함으로써 이루어졌다. 하지만 추력선과 무게중심의 불일치로 인한 모멘트의 발생으로 안정성을 확보할 수 없었다. 이에 안정성을 확보하기 위해 상단과 하단에 댐퍼를 부착한 실내 비행 시험을 통해 날개의 파라메트릭 연구 결과에 대한 간접적인 성능 검증을 수행하였다.

• 한국항공우주학회지
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• 제32권9호
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• pp.27-34
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• 2004

측 추력(Lateral Jet) 제어 시스템에 의해 자세제어를 하는 미사일 주위의 초음속 유동장 해석을 위하여 삼차원 Navier-Stokes 코드 (AADL3D)를 개발하고, 이를 이용한 수치해석 연구를 수행하였다. 미사일의 받음각, 제트 노즐의 위치, 그리고 제트의 분출 각 등의 Parameter가 미사일에 미치는 수직력 및 피칭모멘트에 대한 영향을 알아보기 위한 사례 연구를 수행하였다. 또한 미사일은 무게 중심을 기준으로 4개 영역으로 나뉘어 각 부분에서의 수직력과 모멘트에 대한 기여도를 비교하였다. 공력해석 결과, 각 Parameter 변화에 대한 서로 다른 수직력과 모멘트 변화양상 및 그 원인을 확인할 수 있었다. 또한 각 Parameter 의 적절한 조합에 의해 모멘트 발생을 최소화 할 수 있음을 보여 주었다.

• 한국항공우주학회지
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• 제34권11호
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• pp.1-8
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• 2006

축대칭 발사체의 동적 감쇠계수를 계산하기 위한 정상 예측 방법을 제안한다. 관성좌표계에서 영스핀 코닝 운동을 사용한 정상 해법을 적용하기 위해서는 점성유동 해석이 필수적으로 이루어져야 한다. 제안된 방법을 회전발사체에 적용하여 피칭모멘트와 피치감쇠 모멘트계수를 계산하였다. 결과는 포물형 Navier-Stokes 예측 결과, 실험결과, 비정상 예측 결과와 잘 일치함을 확인하였다. 또한, secant-ogive-cylinder 계열 발사체에 대한 정적 및 동적 계수의 축방향 생성과정을 살펴봄으로써 후방동체의 형상으로 인한 유동 변화가 동적 안정성에 미치는 영향을 고찰하였다.

• 항공우주기술
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• 제4권1호
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• pp.39-44
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• 2005

로터의 성능 예측 검증을 위해 tilt rotor aeroacoustic model(TRAM)에 대한 3차원 CFD 해석을 수행하였고 로터 파워 효과에 의한 영향을 분석하기 위해 수치해석을 행하였다. 수치 기법은 multiple reference method(MRF)와 sliding mesh technique을 사용하였다. TRAM 실험치와 비교 결과 정지 비행시에는 수치해석이 실험보다 적은 추력을 예측하였고 전진 비행시에는 실험결과와 매우 유사한 결과를 예측하였다. 로터효과를 고려한 비행체의 양력은 감소하고 항력 및 피칭 모멘트는 거의 변화가 없는 것으로 판단된다.

• 한국항공운항학회지
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• 제5권1호
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• pp.31-50
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• 1997

A new variable wing that can be swept back and forward synchronously were developed to enhance the aerodynamic and stability characteristics of a high speed airplane. The configuration of the new variable wing changes in such a way that inner part of the wing sweeps forward and outer part of the wing sweeps backward, the shift of aerodynamic center of the wing is small, therfore the static margin that is required for the stability of a airplane is not affected. In this study, various configurations of wing models by combined swept back and forward were designed and a wind tunnel tests were conducted to investigate the aerodynamic characteristics of these variable wings. The experimental results showed that the variable wing by combined swept back and forward has no effect on the pitching moment coefficient affecting on an aircraft stability margin and enhance the aerodynamic characteristics for a given approach angle of attack.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.52-56
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• 2004

Unmanned Aerial Vehicles (UAVs) are remotely piloted or self-piloted aircraft by inputted program in advance or artificial intelligence. In this study Aileron and Elevator are used to control the movement of airplane for horizontal and vertical flights about its longitudinal and lateral axis. In an introduction, the drone was linearly modeled by extracting aerodynamic parameter through flight test and simulation, lift and drag coefficient corresponding to angle of attack, changes of pitching moment coefficient. In the main subject, the flight simulation was performed after constructing hardware using TMS320F2812 from TI company and PID with lateral and longitudinal controller for horizontal and vertical flights. Flying characteristics of two system were estimated and compared through real flight test with hardware equipped algorithm and adaptive algorithm that was applied to consider external factors such as turbulence. In conclusion the control performance of the controller with proposed algorithm was streamlined at lateral and longitudinal controller respectively, we will discuss guidance command to pass way point.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.295-300
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• 2005

The freeplay, one of the concentrated structural nonlinearities, is inevitable for control surfaces of a real air vehicle due to normal wear of components and manufacturing mismatches. Also aerodynamic nonlinearities caused by a shock wave occur in transonic region. In practice, these nonlinearities induce the limit cycle oscillation (LCO) and decrease the transonic flutter speed. In this study, the fictitious mass method is used to apply a modal approach to nonlinear structural models due to freeplay. The transonic small-disturbance (TSD) equation is used to calculate unsteady aerodynamic forces in transonic region. Nonlinear aeroelastic time responses are predicted by the coupled time integration method (CTIM). This method was also applied to a 3D all-movable control wing to investigate its nonlinear aeroelastic responses. The angle of attack effect on the LCO characteristics has been found to be closely related with the initial pitching moment.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.1-8
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• 2009

This is a short review of how CFD contributed to hypersonic flights in the past 50 years. Two unexpected phenomena that occurred in the entry flights of the Apollo and Space Shuttle made us aware of the impact of the high temperature real-gas effects on hypersonic flights: pitching moment anomaly of up to 4 degrees, and radiation overshoot behind a shock wave. The so-called two-temperature nonequilibrium model was introduced to explain these phenomena. CFD techniques were developed to accommodate the two-temperature model. Presently, CFD can predict trim angle of attack to an accuracy of about 1 degree. A concerted effort was made to numerically reproduce the experimentally measured flow-field over a double-cone. As yet, perfect agreement between the experimental data and computation is not achieved. Scramjet technology development is disappointingly slow. The phenomenon of ablation during planetary entries is not yet predicted satisfactorily. In the future, one expects to see more research carried out on planetary entries and space tourism.

• 한국전산유체공학회지
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• 제19권4호
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• pp.94-99
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• 2014

The aerodynamic performance of a modified NACA64-418 with blunt trailing edges of irregular shape was investigated. As the trailing edge of the airfoil was thickened, the drag of the airfoil was increased due to development of a re-circulation bubble in the wake region. To reduce the drag of the airfoil with a blunt trailing edge, the optimum shape of the trailing edge for a modified NACA64-418 was investigated. The numerical results showed that the drag of the protruding shape was much more decreased than that of the retreating shape, but the lift was almost the same regardless of shape. In addition, the pitching moment of the modified NACA64-418 with a protruding sharp trailing edge was the smallest at the given angle of attack.