• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.9
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• pp.829-836
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• 2009

3-Dimensional flow which is represented by horseshoe vortex is generated as a type of secondary flow about the main flow. As well, it causes the flow loss. The present study deals with the leading edge fence shape on a wing-body junction to decrease a horseshoe vortex, one of the main factors to generate the secondary flow losses. The shape of leading-edge fence was optimized with the design variables of the installed height, length, width, and thickness of the fence as the design variables. Approximate optimization design method is used as the optimization. The study was investigated using $FLUENT^{TM}$ and $iSIGHT^{TM}$. Total pressure coefficient of the optimized design case was decreased about 7.5 % compare to the baseline case.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.261-261
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• 2021

자연하천은 직선하천보다 만곡하천으로 존재하는 경우가 많다. 하천의 만곡부에서 2차류 흐름과 나선형 흐름, 원심력이 수충부와 외측제방에 작용하여 하상에 국부적인 세굴이 발생한다. 세굴이 발생하게 되면 수충부나 외측제방에 붕괴나 피해가 일어날 수 있다. 세굴의 피해를 줄이고 만곡부유로를 조정하기 위해 날개형 수제를 설치할 수 있다. 날개형 수제를 설치한 하상은 수제의 두께, 길이, 높이, 간격, 위치, 배열 등에 따라 다르게 반응한다. 본 연구에서는 만곡 개수로에 잠긴 날개형 수제를 설치할 때 만곡 외측에서 수제 열까지의 거리가 만곡부의 유심선 변화에 미치는 영향을 이동상 개수로 수리실험으로 조사하였다. 이동상 수리실험은 폭 1.16 m, 깊이 1 m, 길이 24 m인 90° 만곡 개수로에 d₅₀이 3.3mm인 잔자갈을 깔아 하상경사 1/300로 정리한 후 수제를 설치하는 순서로 이루어졌다. 수제는 폭 20mm, 길이 70mm의 직사각형 단면 목재로 제작하여 설치하였고, 실험별 이격거리는 외측 제방으로부터 8.4 cm, 14 cm, 19.6 cm로 하였다. 실험유량은 140l/s로 3시간 동안 흘린 뒤 하상측정장치를 이용하여 주요 횡단면별 하상고를 측정하였다. 측정한 데이터를 이용하여 최심하상고의 크기와 위치, 유심선의 변화 등을 분석하였다.

• Korean journal of applied entomology
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• v.62 no.3
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• pp.117-124
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• 2023

The management of Ricania spp. is difficult because this pest has a wide host range and diverse habitats such as agricultural, suburban, urban, and forested areas. However, the researches for Ricania spp. management have been focused on only agricultural crops. Thus, it is required to determine the arboreal host preference of Ricania spp. at the surrounding areas of the farms to increase its management efficiency. To determine its host preference at arboreal plants, we reviewed the previous studies and investigated the densities of Ricania spp. at woody plants with high ecological importance but insufficiently studied. This study identified 120 species in 53 families of arboreal hosts of Ricania spp. Only Cornus officinalis and Styrax japonicus were preferred by all developmental stages of Ricania spp. The host preference of Ricania spp. was changed according to its developmental stages. This phenomenon would be caused by that each developmental stage of Ricania spp. would prefer different parts of woody plant, and require different nutrients for its survivor and reproduction. These results of this study could be helpful to make a plan of comprehensive management strategies for Ricania spp.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.6
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• pp.530-536
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• 2010

In-flight icing is a critical technical issue for aircraft safety and, in particular, ice accretions on aircraft surfaces can drastically impair aerodynamic performances and control authority. In order to investigate icing effects on the aerodynamic characteristics of KC-100 aircraft, a state-of-the-art CFD code, FENSAP-ICE, was used. A main wing section and full configuration of KC-100 aircraft were considered for the icing analysis. Also, shapes of iced area were calculated for the design of anti-/de-icing devices. The iced areas around leading edge of main wing and horizontal tail wing were observed maximum 7.07% and 11.2% of the chord length of wing section, respectively. In case of wind shield, 16.7% of its area turned out to be covered by ice. The lift of KC-100 aircraft were decreased to 64.3%, while the drag was increased to 55.2%.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.5
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• pp.625-636
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• 2019

Recently, research on projectiles with wings for precision guidance is actively underway. In this study, we analyzed how the tail fins attached to the projectile affect the base drag. Aerodynamic analysis was performed with RANS(Reynolds Averaged Navier-Stokes) equations using FLUENT, a commercial CFD(Computational Fluid Dynamics) code. Through the aerodynamic analysis, the base drag characteristics of the projectile by parameters (number, length, thickness, position, shape of tail fin) were investigated. The results of this study are expected to be applicable to aerodynamic design of tail fins mounted on projectiles.

• Journal of Korean Association for Spatial Structures
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• v.19 no.3
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• pp.14-22
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• 2019

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.2
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• pp.108-114
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• 2002

In this paper, nonlinear finite element analysis is performed to ensure structural safety and to suggest the design improvement of wing-to-fuselage joint of the KSR-III rocket. In the joint, wings are attached to fuselage by fitting wing attachment part into the groove on the fuselage frame, and load transfer between wing and fuselage frame is accomplished mainly throug the contact of two members as well as fastening bolts. The careful finite element modeling has been proposed for the purpose of analyzing problems with relatively complicated load path. The detailed bolt modeling is conducted and GAP elemets are used to simulate contact problem between joined members and bolts. The suggested design improvement is verified by structural testing and the analysis results are compared with test results.

• Composites Research
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• v.30 no.1
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• pp.52-58
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• 2017

This paper presents the optimum design methodology for composite wing structure which automatically calculates the safety margin using optimization framework integrating failure modes. Particularly, its framework is possible to optimize sizing procedure to prevent failure mode which has the greatest effect on reducing the sizing time of composite structure. The main failure mode was set as the first ply failure, buckling failure mode, and bolted joint stress field, and the margin was calculated to minimize the weight. The design variable is a laminate sequence database and the responses are strain, buckling, bolted joint stress field. The objective function is the mass of the wing structure. The results of buckling analysis were compared using the finite element model to verify the robustness and reliability of Composite Optimizer.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.2
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• pp.135-142
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• 2021

In this work, multi-turn wings and guide plates are installed on recycled aggregate crushing devices to improve existing low recycled aggregate quality. Simulation analysis to evaluate the crushing efficiency of the new device shows enhanced crushing efficiency since the installation of guide plates shreds most of the inputs inside the crushing drum, and the multi-turn wings and guide plates induce rebound and circulation of the aggregate. Through this, the new device was found to be more economical and efficient than the existing recycled aggregate crushing device. Also, the amount of cement paste and mortar attached to the surface of the aggregate was smaller than that of the existing recycled aggregate, and it was found that the mechanical properties and elastic modulus deterioration were reduced. However, the carbonation resistance of concrete was not improved to the level of natural aggregates due to the remaining tiny cement paste and mortar on the surface of the new recycled aggregate. Therefore, it is deemed necessary to further research and experiment such as device improvement or binder development to reduce durability degradation of concrete mixed with new recycled aggregate.

• Korean journal of applied entomology
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• v.44 no.2
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• pp.91-95
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• 2005

This study was conducted to investigate the morphological characteristics, overwintering sites and behavior for each stage of Oligota kashmirica benefica (Coleoptera: Sthphylinidae). Egg was oval type, yellow, 0.3 mm size. Larva exuviated 3 times and the last (3rd) instar, length 1.6 mm, wide 0.4 mm, became dermata pupa in soil. Adult was lightish dark-brown, and coriaceous forewing covered a half of abdomen. O. kashmirica benefca mainly overwinters with adult at Japanese cedar (Cryptomeria japonica) windbreaks of orchards, but it did not diapause in greenhouse during winter.