• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 추계학술대회 논문집
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• pp.227-228
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• 2010

• 한국항공우주학회지
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• 제37권8호
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• pp.729-736
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• 2009

벌새(Selasphorus rufus)의 날갯짓 운동에 의한 양력발생 및 추력발생 메커니즘을 이해하고자 2차원 수치해석을 수행하였다. 날갯짓 운동의 궤적은 풍동 실험에서 관찰된 결과를 모델링하여 해석하였다. 비행속도에 따라 날갯짓 운동 궤적이 달라지고, 그 결과 양력 및 추력의 발생 메커니즘이 변화하는 것을 알 수 있었다. 본 연구에서는 이를 통하여 비행속도를 저속비행과 고속비행으로 구분하여 물리적인 이해를 하고자 하였다. 양력발생의 경우에는 기존의 날갯짓 비행의 주된 양력발생 메커니즘인 앞전와류효과(Leading Edge Vortex Effect), 실속지연(Delayed Stall), 후류포착(Wake capture)등의 메커니즘을 확인하였으며, 벌새에서 유일하게 관찰되는 Upstroke에서의 양력발생 메커니즘을 유동특성 분석을 통하여 확인하였다. 추력발생의 경우에는 벌새의 골격 구조, 와류형성 및 압력구배에 따른 합력 성분의 분해를 통하여 이해할 수 있었다.

• 한국항공우주학회지
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• 제34권8호
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• pp.55-62
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• 2006

본 논문에서는 단일층 압전 작동기로 구동되는 곤충 모방 날갯짓 기구의 실험적 평가의 결과를 제시하였다. 변위 증폭기구의 연결막대 길이와 힌지 위치를 조절하여, 말벌류 곤충의 상향 날갯짓 끝에 발생하는 날개 겹침 (clap)을 모방할 수 있도록 하였다. 또한, 실제 곤충 날개의 단면이 지그-재그형인 것을 모방한 날개를 제작하여 부착하였다. 이 두 가지 추가적인 고안으로 인하여 본 날갯짓 기구는 이전 날개에 비하여 면적이 절반 밖에 되지 않음에도 불구하고 더 큰 양력을 발생할 수 있었다. 본 연구에서는 날개의 겹침, 지그-재그형 단면, 인가전압 파형이 양력 발생에 미치는 영향을 조사하였다. 최종적으로는 디지털 고속카메라를 이용하여, 개선된 날갯짓 기구가 상향 날갯짓과 하향 날갯짓에서 와류를 발생함을 확인하였다.

• 한국가시화정보학회지
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• 제8권2호
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• pp.16-22
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• 2010

A flow visualization has been conducted to investigate unsteady flight characteristics of a model of dragonfly. The mechanism of lift generation by flapping wings is analyzed using smoke-wire and high speed camera. The experimental results of flow visualization show a discernible sequential dynamics that three mechanisms and high incidence angle of the wings are responsible for the lift generation. The leading edge vortex by the rapid acceleration of leading edge of the wing during initial stage of stroke causes a strong lift enhancement. Delayed stall during the stroke, fast supination and pronation of the wing near the end of each stroke are also responsible for the lift generation.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.709-712
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• 2003

The existing technical limitation makes engineer imitate nature to solve engineering problems. Recently Micro Air Vehicle(MAV) imitating the mechanism of birds or insects is being developed. Especially Ultra Flite supported by DARPA is studying hummingbird aerodynamics to relate that information to MAV. To drive MAV bender piezoelectric(PZT) actuators are used due to the convinience of control and the small size. But the displacement of the PZT actuators are very small, and the wing driving mechanism which amplifies the stroke generated by the PZT actuators has constraints in design and manufacture because of the small dimension. In this paper a wing design concept and a efficient driving mechanism are proposed. Electroactive polymers(EAPs) are used as wing mechanism actuators. Using OpenGL the mechanisms are simulated graphically. Also a prototype actuator is being developed and verified by digital Mockup with CATIA. Basic kinematics of the mechanism is studied.

• 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.

• International Journal of Industrial Entomology and Biomaterials
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• 제1권2호
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• pp.91-93
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• 2000

Insects have many excellent features and functions in their small bodies, such as hexapod walking, flapping flight, vision systems, sensory hairs, etc, and those characteristics can be thought as good models for many types of robots. Insects also will be good models far micro-machines because of its size. Insect behavior consists of simple reflex acts and programmed behavior, Some robots were made in order to clarify the emergent mechanism of insect behavior, Through some experiments it would be found that even if insect behavior consists of some simple action patterns, it looks intelligent through interactions its sensors and actuators with its complex environment. In the near futures small robots inspired by insects will be used in many fields of our life. I hope that insect-model based robots will play an active part in many fields and that they will make us happy.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 추계 학술대회논문집
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• pp.126-129
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• 2006

Many researchers have made an effort to explain flight mechanism of flapping insects. As a result, several unsteady mechanisms about lift generation in insect flight have been proposed. But it has a limits to elucidate insect's forward flight and abrupt thrust, because most of these are about insect's hovering flight. For this reason, the objective of this paper is to simulate "Figure-of-eight motion" of insect's wing during tethered flight for comprehending aerodynamic property in insect's forward flight.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.384-388
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• 2007

Aerodynamic characteristics of Coleoptera species of Epilachna quadricollis and Allomyrina dichotoma are experimentally and numerically investigated. Using digital high speed camera and smoke wire technique, we visualized the continuous wing kinematics and the flight motion of free-flying coleoptera. The experimental visualization shows that the elytra flapped concurrently with the main wing both in the downstroke and upstroke motions. The wing motion of Epilachna quadricollis was captured and analyzed frame by frame to identify the kinematics of the wings and to implement it in the movement of a model wing (thin plate) in the simulation. The two-dimensional simulation of Epilachna quadricollis hovering flight was performed by assuming the wing cross section shape as a thin plate, even though most of insect's wings are made of curved corrugated membrane. The effect of Reynolds number are investigated by the simulation. Meanwhile, in order to investigate the role and effect of elytra, the flow visualization of Allomyrina dichotoma was carried on using smoke wire visualization technique. Here, we confirmed that the vortex generated by elytra due to its movement is strongly influence the vortex dynamic generated by hind wings.

• Wind and Structures
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• 제32권2호
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• pp.105-114
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• 2021

This paper describes a wind tunnel test on a 1:25 scale model of TTU building with several adjustable openings in order to comprehensively study the characteristics of fluctuating internal pressures, especially the phenomenon of the increase in fluctuating internal pressures induced by tangential flow over building openings and the mechanism causing that. The effects of several factors, such as wind angle, turbulence intensity, opening location, opening size, opening shape and background porosity on the fluctuating internal pressures at oblique wind angles are also described. It has been found that there is a large increase in the fluctuating internal pressures at certain oblique wind angles (typically around 60° to 80°). These fluctuations are greater than those produced by the flow normal to the opening when the turbulence intensity is low. It is demonstrated that the internal pressure resonances induced by the external pressure fluctuations emanating from flapping shear layers on the sidewall downstream of the windward corner are responsible for the increase in the fluctuating internal pressures. Furthermore, the test results show that apart from the opening shape, all the other factors influence the fluctuating internal pressures and the internal pressure resonances at oblique wind angles to varying degrees.