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잠자리유형 모델의 추력 및 양력생성에 관한 실험적 연구
김송학,장조원,Kim, Song-Hak,Chang, Jo-Won 한국군사과학기술학회 2006 한국군사과학기술학회지 Vol.9 No.4
An experimental study was carried out in order to investigate the effects on the fore- and hind-wings of a dragonfly-type model. A model with two pairs of wing was developed to measure the lift and thrust of a dragonfly-type model. The fore-wing and hind-wing had incidences angle of $0^{\circ}\;and\;10^{\circ}$. The freestream velocity is 1.6m/sec and the corresponding chord Reynolds number was $Re=2.88{\times}10^3$. Also, these experiments were carried out with a phase difference of $90^{\circ}$ between the fore- and hind-wing, aerodynamic forces caused by fore-wing only and two pairs of wings were investigated according to the reduced frequency. The results show that the model with fore-wings only generates a thrust component; however, the dragonfly-type model with hind-wings with an incidence angle of $10^{\circ}$ generates a drag component. The total drag is also increased with reduced frequency due to the increased lift of hind-wings.
잠자리 유형 모델의 앞ㆍ뒤 날개 위상차에 대한 공력연구
김송학(Song-Hak Kim),장조원(Jo-Won Chang),송병흠(Byung-Heum Song) 한국항공우주학회 2006 韓國航空宇宙學會誌 Vol.34 No.11
비정상 공기력 측정이 두 쌍의 날개를 갖는 잠자리 유형 모델의 위상차에 따른 효과를 조사하기 위하여 수행되었다 잠자리 유형 모델의 플런징 운동에 의하여 발생된 공기역학 적인 힘을 측정하기 위하여 로드셀을 사용하였다. 본 잠자리 유형 모델은 실제 잠자리와 동역학적으로 상사하며,앞ㆍ 뒤날개는 각각 0˚의 10˚의 붙임각(incidence angle)을 가지고 있다. 다른 실험 조건은 다음과 같다. 자유류의 속도는 1.6 m/sec이고, 이와 관련된 시위 레이놀즈수 2.88x10이며, 앞 ㆍ 뒤날개의 위상차는 각각 0˚,90˚,180˚, 그리고 270˚이다. 잠자리 유형 날개의 한 주기 동안 공기역학적 계수의 변화가 제시되었다. 연구 결과는 잠자리 유형 모델의 양력은 앞 ㆍ 뒤날개가 downstroke 운동을 수행할 때 발생되며, 뒷날개가 downstroke 운동과정을 수행하면 양력 발생과 함께 항력도 발생한다는 것을 보여준다. Unsteady aerodynamic force measurements were carried out in order to investigate the effects of phase difference of a dragonfly-type model with two pairs of wing. A load-cell was employed to measure the aerodynamic force generated by a plunging motion of the dragonfly-type model. The dragonfly-type model has a dynamic similarity with real one, and incidence angles of fore- and hind-wing are 0˚ and 10˚, respectively. Other experimental conditions are as follows: The freestream velocity was 1.6 m/sec and corresponding chord Reynolds number was 2.88×10³, and phase differences of fore- and hind-wing were 0˚, 90˚, 180˚ and 270˚. The variation of aerodynamic coefficients during one cycle of the wing motion is presented. Results show that the lift is generated during the downstroke motion and the drag generated during the hind-wing's downstroke motion with the lift generation.
김송학(Song Hak Kim),장조원(Jo Won Chang) 한국가시화정보학회 2004 한국가시화정보학회지 Vol.2 No.2
The purpose of this visualization study is to investigate the effect of reduced frequency qualitatively by examining wake patterns for dragonfly flight motion. Dragonflies have two pairs of wing (a forewing and hindwing) and flight is achieved by a pitching and plunging, so it makes a separation over the wings. The separation affects the wake pattern and changed wake pattern has an influence on lift, drag, and propulsion. This experiment was conducted by using a smoke wire technique and a camera fixed above the test section used to take a photograph of the wake. An electronic device is mounted below the test section to find the exact mean positional angle of the wing. The reduced frequency in the experiment is 0.15, 0.3 and 0.45. Results show that reduced frequency is closely related to the wake pattern that determines flight efficiency.
김송학(Song Hak Kim),김현석(Hyun Seok Kim),장조원(Jo Won Chang),부준홍(Joon Hong Boo) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
Flow visualization experiments have been performed to investigate the effects of phase lag, reduced frequency qualitatively by examining wake pattern on a dragonfly type wing. The model was built with a scaled-up, flapping wings, composed of paired wings with fore- and hindwing in tandem, that mimicked the wing form of a dragonfly. The present study was conducted by using the smoke-wire technique, and an electronic device was mounted to find the exact positional angle of wing below the tandem wings, which amplitude is ranged from -16.5° to +22.8°. Phase lag applied on the wings is 0°, 90°, 180° and 270°. The reduced frequency is 0.15, 0.3 and 0.45 to investigate the effect of reduced frequency. It is inferred through observed wake pattern that the phase lag clearly plays an important role in the wake structures and in the flight efficiency as changing the interaction of wings. The reduced frequency also is closely related to wake pattern and determines flight efficiency.