• 제목/요약/키워드: angle of incidence

검색결과 587건 처리시간 0.028초

잠자리 모사 모형 주변의 유동가시화 실험 (Flow Visualization on the Bio-Mimic Model of Dragonfly)

  • 윤준용;엄상진;지영무;박준상
    • 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.

벨벳직물(織物)의 외관특성(外觀特性)과 파일섬유(纖維)의 삼차원적(三次元的)모델링 (Appearance Characteristics of a Velvet Fabric and 3-Dimensional Modeling of Pile Fibers)

  • 김종준;전동원;이정민
    • 패션비즈니스
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    • 제9권4호
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    • pp.170-177
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    • 2005
  • Velvet fabric has soft touch, subtle luster, and good draping property. Threedimensional simulated models of cylindrical monofilaments constituting the velvet fabric were prepared. Image analysis techniques were used to measure the reflected light from the surface of velvet fabrics and the simulated images of the pile fibers. As the angle of incidence increased, the reflectance from the velvet surface became lower. Most of the reflection came from the tips of the cut piles. Crushed velvet type also was modeled using slant cylinder models on top of a base plate.

Cause of Cavitation Instabilities in Three Dimensional Inducer

  • Kang, Dong-Hyuk;Yonezawa, Koichi;Horiguchi, Hironori;Kawata, Yutaka;Tsujimoto, Yoshinobu
    • International Journal of Fluid Machinery and Systems
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    • 제2권3호
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    • pp.206-214
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    • 2009
  • Alternate blade cavitation, rotating cavitation and cavitation surge in rocket turbopump inducers were simulated by a three dimensional commercial CFD code. In order to clarify the cause of cavitation instabilities, the velocity disturbance caused by cavitation was obtained by subtracting the velocity vector under non-cavitating condition from that under cavitating condition. It was found that there exists a disturbance flow towards the trailing edge of the tip cavity. This flow has an axial flow component towards downstream which reduces the incidence angle to the next blade. It was found that all of the cavitation instabilities start to occur when this flow starts to interact with the leading edge of the next blade. The existence of the disturbance flow was validated by experiments.

폴리이미드막에 편광되지 않은 UV광을 경사지게 조사한 광배향 TN-LCD의 전기광학특성에 관한 연구 (EO performance of photo-aligned TN-LCD with oblique non-polarized UV light irradiation on polymer surface)

  • 서대식;박태규;한정민;박두석;황율연
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1998년도 하계학술대회 논문집 D
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    • pp.1385-1387
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    • 1998
  • In this paper, we studied the electro-optical(EO) performance of photo-aligned twisted nematic(TN)-liquid crystal display(LCD) with oblique non-polarized ultraviolet (UV) light irradiation on polyimide (PI) surface. The monodomain alignment of photo-aligned TN-LCD is obtained with an angle of incidence of $85^{\circ}$ on PI surface. Also, we observed that the voltage transmittance and response time characteristics of photo-aligned TN-LCD is almost same compared to rubbing treated TN-LCD. Finally, we measured that the voltage-holding-ratio(VHR) of photo-aligned TN-LCD is almost same compared to rubbing treated TN-LCD.

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Optical Setup for Full-Field Imaging Test of MATS Limb Telescope

  • Lee, Sunwoo;Hammar, Arvid;Park, Woojin;Chang, Seunghyuk;Pak, Soojong
    • 천문학회보
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    • 제43권1호
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    • pp.68.3-68.3
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    • 2018
  • The MATS (Mesosphere Airglow / Aerosol Tomography Spectroscopy) satellite is a Swedish scientific microsatellite which Kyung Hee University participates in developing. The limb telescope of the MATS satellite is designed with linear astigmatism-free off axis optical configuration which allows wide field of view ($5.67^{\circ}{\times}0.91^{\circ}$). Here we present the full-field optical performance test setup that consists of a point source, a collimator, the limb telescope and a CCD (Charged Coupled Device). The incidence angle of the collimator was carefully controlled by the rotary stage under the limb telescope. The imaging tests represent expected results without dominant aberrations.

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Lateral Resolution Enhancement in Confocal Self-interference Microscopy with Commercial Calcite Plate

  • Kang DongKyun;Yoo HongKi;Lee SeungWoo;Gweon Dae-Gab
    • Journal of the Optical Society of Korea
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    • 제9권1호
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    • pp.32-35
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    • 2005
  • In light microscopy, spatial resolution is limited by diffraction effect. Confocal microscopy has improved resolutions in both lateral and axial directions, but these are still limited by diffraction effect. Confocal self-interference microscopy (CSIM) uses interference between two perpendicularly polarized beams to enhance lateral resolution. In previous research, we proposed a calcite plate with its optic-axis perpendicular to the propagation angle and one of the boundary surfaces of the plate. This type of plate is not widely used to our knowledge. In this paper, we change the calcite plate to more common one, which is commercially available. This calcite plate has its optic axis in the plane of incidence. We analyze the characteristics of this calcite plate and numerically compare the performances of CSIM in previous research and CSIM with the commercial calcite plate. Numerical results show improved performance when using the commercial calcite plate

공명기 분포에 따른 공명기 배열형 패널의 공명주파수 변화 (Resonance frequency shifts of Helmholtz resonator array panel brought by change in resonator arrangements)

  • 김상렬;김양한
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2005년도 추계 학술대회논문집(수송기계편)
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    • pp.97-100
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    • 2005
  • Precise prediction of resonance frequency has been the subject of numerous papers related to Helmholtz resonator design because of its high performance at the frequency. The resonance frequency is dependent upon not only the internal dimensions of resonator but also the external boundary conditions such as the existence of other resonators in Helmholtz resonator array panel. However, the latter effect, which changes the external end correction of resonator, has not been well studied. We propose a formula to calculate the radiation impedance (or external end correction) of Helmhoitz resonator array panel. Any distance between adjacent resonators and any angle of Incidence can be allowed in the method. Numerical examples show how and how much the distance affects the resonance frequency of the panel. It is also found that the maximum absorption of the panel varies with the resonator arrangement.

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접지된 유전체 슬랩 도파로에서 주기적인 임의 형태의 격자에 의한 표면파 산란 (Surface wave scattering by finite periodic gratings of an arbitrary profile in a grounded plane)

  • 이철훈;조웅희;조영기
    • 대한전자공학회논문지TC
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    • 제37권11호
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    • pp.1-7
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    • 2000
  • Surface wave scattering by periodic grooves of arbitrary profile in a grounded dielectric slab is investigated for the TE surface wave incidence. Both the finite and infinite periodic geometries are considered. The former case is analyzed by using of hybrid FEM/MOM and the latter by using of full MOM procedure. Some numerical results for the reflected and transmitted powers in a grounded dielectric slab, radiation power into the free space, and radiation patterns in case of finite structure and for the dispersion diagram in case of infinite structure are presented. And some descriptions on the relationship between the finite and infinite structure such as the maximum beam angle are given.

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자연환기 벤틸레이터 형태에 따른 환기효율 평가 (Evaluation of Ventilation Efficiency for Various Gravity Ventilators)

  • 하현철;김태형
    • 설비공학논문집
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    • 제14권7호
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    • pp.543-551
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    • 2002
  • Gravity ventilators allow the escape of the warm air and air contaminants due to both (either) buoyancy and (or) convection. As a natural ventilation strategy, various gravity ventilators can be installed on the roof. Ventilation efficiency could be affected by various parameters, such as, area of openings, wind velocity and incidence angle, temperature difference between inside and outside, and shape of ventilator. Especially, the shape of roof gravity ventilator might be one of influencing factors for the effective ventilation. The window type gravity ventilators are frequently installed instead of general (standard) gravity ventilator. However, the ventilation efficiencies of them were not proved yet. To compare the ventilation efficiency, general type ventilator and two window type ventilators were numerically tested. Mean age of air, temperature and CO concentration were predicted by using commercial CFD code, AIRPAK (Ver. 2.0) with various conditions. The predicted result showed that general type ventilator is more effective for natural ventilation than window type ventilators.

브레이드 외형(外形)이 풍력(風力) 터어빈의 공력(空力) 성능(性能)에 미치는 영향 (Aerodynamic Performance of a Wind-Turbine Affected by Blade Configuration)

  • 손병찬
    • 태양에너지
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    • 제6권2호
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    • pp.86-92
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    • 1986
  • This paper presents the aerodynamic performances of horizontal axis wind turbines with non-twisted but taperd blades. Five configurations of blades, namely, one straight blade and four tapered blades with taper ratio of ranging from 0.1 to 0.7 have been simulated. The aerodynamic performances of the wind turbines have been determined over blade incidence angle of ranging from $2^{\circ}$ to $6^{\circ}$ and keeping same solidity and radius of them. The results are presented comparing straight blade from four tapered blades for maximum power coefficient and tip looses against variation of taper ratio. It also shows that the wind turbine with taper ratio of 0.5 has the highest maximum power coefficient than others. And wind turbines with taper ratio below 0.2 have lower values of maximum power coefficients than straight one. The tip loss of straight blade is the largest and reduces Slightly with the decrementation of taper ratio.

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