• 한국유체기계학회 논문집
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• 제13권2호
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• pp.41-47
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• 2010

The effect of incidence angle on the three-dimensional flow and aerodynamic loss in the tip leakage flow region downstream of a turbine rotor cascade has been investigated for two tip gap-to-chord ratios of h/c=0.0% (no tip gap) and 2.0%. The incidence angle is changed to be $i=-10^{\circ}$, $0^{\circ}$, and $5^{\circ}$. The results show that for $i=5^{\circ}$, secondary flows including the passage vortex are intensified noticeably, and there is a strong interaction between the passage and tip leakage vortices. For $i=-10^{\circ}$, however, the passage vortex is weakened significantly, so that there exists only a strong leakage-jet-like secondary flows near the casing wall. For h/c=0.0% and 2.0%, aerodynamic loss tends to increase with increasing i from $-10^{\circ}$ to $5^{\circ}$. A small increment of i in its positive incidence range results in a remarkable aerodynamic loss increase, while increasing i in the negative incidence range leads to a small change in the aerodynamic loss generation.

• Earthquakes and Structures
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• 제8권5호
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• pp.1127-1146
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• 2015

The excitation angle or angle of incidence is the angle in which the horizontal seismic components are applied with respect to the principal structural axes during a time history analysis. In this study, numerical simulations and parametric studies are performed for the investigation of the effect of the angle of seismic incidence on the response of adjacent buildings, which may experience structural pounding during strong earthquakes due to insufficient or no separation distance between them. A specially developed software application has been used that implements a simple and efficient methodology, according to which buildings are modelled in three dimensions and potential impacts are simulated using a novel impact model that takes into account the arbitrary location of impacts and the geometry at the point of impact. Two typical multi-storey buildings and a set of earthquake records have been used in the performed analyses. The results of the conducted parametric studies reveal that it is very important to consider the arbitrary direction of the ground motion with respect to the structural axes of the simulated buildings, especially during pounding, since, in many cases, the detrimental effects of pounding become more pronounced for an excitation angle different from the commonly examined 0 or 90 degrees.

• Journal of the Optical Society of Korea
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• 제16권1호
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• pp.6-12
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• 2012

We present the optical models and calculation results of thin-film organic solar cells (OSCs) at oblique incidence of light, using the transfer matrix method. The simple expression for the optical power dissipation is derived at oblique incidence for s- and p-polarized light. The spatial distribution of the electric field intensity, the optical power density, and the optical power dissipation are calculated in both s- and p-polarized light with respect to the incidence angle. We identify how the light absorption efficiency for p-polarized light becomes relatively larger than that for s-polarized light as the incidence angle increases.

• 한국소음진동공학회논문집
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• 제20권3호
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• pp.296-307
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• 2010

This paper deals with the energy transmission ratio of the elastic waves transmitting through a solid wall. Based on the displacement of the reflected and transmitted waves relative to the incident waves, the energy transmission ratio of the wave was obtained by multiplying the vibration velocity and stresses. Numerical calculation provided with the transmission ratio and refraction angle corresponding to the incidence angle, and it showed the mode conversion from the incident longitudinal wave to the transmitted transverse wave in particular incidence angle range. The paper established a procedure to find the incidence angle of the maximum energy transmission ratio and confirmed it by experiment.

• 한국콘텐츠학회논문지
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• 제19권6호
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• pp.471-480
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• 2019

정상인을 대상으로 체질량지수, 전만각도에 따른 L-spine 3~4, L-spine 4~5, L-spine 5~Sacrum 1의 각각의 추간판각도를 비교 분석하여 입사각을 제시하였다. 체질량지수의 L-spine 3~4, L-spine 4~5, L-spine 5~Sacrum 1의 정면 입사각도는 머리 쪽 방향으로 5.66도, 13.23도, 29.13도였으며, 전만각도의 L-spine 3~4, L-spine 4~5, L-spine 5~Sacrum 1의 정면 입사각도는 머리 쪽 방향으로 6.32도, 16.09도, 35.36도였다. 체질량지수, 전만각도에 따른 정면 입사각도에 따라 적용한 팬텀의 일반 전후방향 영상의 왜곡정도를 면적비율로 비교한 결과 L-spine 4~5, L-spine 5~Sacrum 1의 추간판각도에서 유의미한 차이가 있었고(p<0.05), 전만각도와 추간판각도는 양의 상관관계를 보였다(p<0.05). 팬텀의 전만각도에 따른 추간판각도 계측 값을 머리 쪽 방향으로 입사각을 L4는 11도, L5는 26도로 적용하여 영상의 유용성을 평가한 결과, 왜곡비율면적은 L4에서 14.90%에서 12.11%로 줄어들었고, L5에서는 15.25%에서 13.72%로 줄어들었다. 계측된 추간판 각도에 따른 입사각을 적용한 허리뼈 일반 전후방향 영상에서 허리뼈 4번, 5번을 목적으로 하는 허리뼈 정면 영상에서 왜곡을 줄여, 정확한 구조의 정면 추체상과 인접하는 관절 간 영상을 얻을 수 있었고, 목적하는 부위의 영상의 질과 진단적 정보를 향상시킬 수 있었다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2001년도 유체기계 연구개발 발표회 논문집
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• pp.30-34
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• 2001

In the present study, we studied the method of predicting the on-design and on-design point performance of axial flow fan with adjustable pitch blades. With the change of stagger angle of axial flow fan with adjustable pitch blade, flow rate and pressure can be changed. Because of this merit adjustable pitch fans are used in many industrial facility. When changing stagger angle or estimating the performance at a wide range of off-design condition, incidence angle changes greatly as the flow rate changes. Therefore, the deviation angle at the blade exit is estimated by the correlation considering the effects of blade design, incidence angle variation. In the loss model, we used known pressure loss model for blade boundary layer and wake, secondary flow, endwall boundary layer and tip leakage flow. The results of modified deviation angle model and experiment were compared for the usefulness of the modified model.

• 설비공학논문집
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• 제17권7호
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• pp.659-668
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• 2005

The thermal performances of glass evacuated tube solar collectors are numerically investigated. Four different shapes of solar collectors are considered and the performances of these solar collectors are numerically investigated. Dealing with only collecting tube, the effects of not only the shape of the absorber tube but also the incidence angle of solar irradiation on the thermal performance of the collector are studied because the energy obtained by the absorber can be varied according to the incidence angle of solar radiation. However, the solar irradiation consists of the beam radiation as well as the diffuse radiation. Also, in actual system, the interference of solar irradiation and heat transfer interaction between the tubes should be considered. Therefore, this study considered these effects is carried out experimentally and numerically. The accuracy of the numerical model is verified by experiments. The result shows that the thermal performance of the absorber used a plate fin and U-tube is about $25\%$ better than those of the other models.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권1호
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• pp.100-113
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• 2017

Snap rolling during hard turning and instability during emergency rising are important features of submarine operation. Hydrodynamics modeling using a high incidence flow angle is required to predict these phenomena. In the present study, a quasi-steady dynamics model of a submarine suitable for high-incidence-angle maneuvering applications is developed. To determine the hydrodynamic coefficients of the model, static tests, dynamic tests, and control surface tests were conducted in a towing tank and wind tunnel. The towing tank test is conducted utilizing a Reynolds number of $3.12{\times}10^6$, and the wind tunnel test is performed utilizing a Reynolds number of $5.11{\times}10^6$. In addition, least squares, golden section search, and surface fitting using polynomial models were used to analyze the experimental results. The obtained coefficients are presented in tabular form and can be used for various purposes such as hard turning simulation, emergency rising simulation, and controller design.

• 한국태양에너지학회 논문집
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• 제24권1호
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• pp.39-45
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• 2004

The thermal performance of glass evacuated tube solar collectors with finned tubes is numerically modelled with code and investigated to see the effect of toe inner tube diameter and incidence angle. The solar collector consists of a two-layered glass tube and an inner tube. Finned tubes are used as the inner tube of the collector in order to improve the performance of the solar collector. Two strip-type fins are attached on the opposite sides of the inner tube surface. The fin is wide enough to be tightly fatted inside the glass tube. The results show that if the incidence angle is small, the effect of the tube diameters is not significant on the thermal performance and the outlet air temperature. If the incidence angle is large, however, the outlet air temperature and the performance increases as the inner tube diameter increases.

• 한국추진공학회지
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• 제5권2호
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• pp.24-31
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• 2001

본 연구에서 축류형 터빈의 설계기술이 개발되었다. 설계를 위하여 우선적으로 기본형상에 대한 설계가 이루어졌으며 유선곡률법에 의하여 터빈 내부유로에서의 공기 물성치를 계산하였다. 계산된 여러 유로에서의 유동각들을 고려하여 익형의 형상을 설계하기 위한 설계변수들이 설정되었다. 설정된 형상변수로부터 정익은 C4 형상을 사용하여 설계되었으며 동익은 설계변수에 의하여 설계되었다. 정익은 일체형으로 제작되었으며 동익은 입사각의 변경에 따른 실험을 수행하기 위하여 분리형으로 제작하였다. 터빈입구에서의 공기력과 RPM에 따라서 터빈에서의 출력이 얻어졌으며 실험의 결과는 제작된 터빈이 반동터빈임에도 불구하고 입사각이 줄어드는 것에 비례하여 출력이 감소하는 현상을 보여주었으며 설계값에서 입사각이 7.5도 감소함에 따라 5%의 효율 감소가 발생되었다.