• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
• /
• pp.253-256
• /
• 2006

For nuclear concrete structures on the coast, the prevention and management against salt damage is needed because they are being under the influence of the sea water at all times. In general, the deterioration of the concrete is generated in concrete surface firstly and then extended into concrete gradually as its service life increases. Therefore, the protective layer on the concrete surface is needed to establish and manage the durability of concrete. To enhance the durability performance of the existing and new concrete, the development and application of a high-performance penetration sealer is needed. The sealer has to have the functions that are able to prevent the attack of the moisture, carbon dioxide, and harmful substance from the outside. Therefore, the aim of this project is to guarantee the long service-life and waterproof performance of a nuclear concrete structures by increasing the density of the existing and new concrete surface layer, and to enhance the dust-proof performance of the uncoating part of the nuclear safety-relative structures.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 추계학술대회논문집B
• /
• pp.388-393
• /
• 2001

An experimental study is conducted to investigate the interaction of vortices over a delta wing with leading edge extension(LEX) through the off-surface flow visualization and the 5-hole probe measurements of the wing wake region. Especially, the application of a new visualization technique is employed by ultrasonic humidifier water droplet and laser beam sheet. The results, both the off-surface visualization and the 5-hole probe, show that LEX tends to stabilize the vortices of the delta wing up to the high angle of attack even though the model is yawed. With increasing yaw, the windward leading edge vortex moves inward, and closer to the wing surface, while the leeward vortex moves outwards and away from the wing surface. The vortex interaction is promoted in the windward side, and is delayed in the leeward side.

• 대한조선학회논문집
• /
• 제35권3호
• /
• pp.14-25
• /
• 1998

본 논문은 자유수면 위를 가까이 비행하는 표면효과익선(Wing-in Ground Effect Craft)의 날개에 작용하는 정상(steady) 및 비정상(unsteady) 동유체력을 포텐셜 기저 패널법을 사용하여 수치해석을 수행한 결과이다. 파가 없는 고정수면 위를 비행하는 정상문제의 경우에 대해서는 단면변화, 앙각(angle of attack), 가로-세로비(aspect ratio), 날개 끝단판(end-plate)의 부착 유무 및 비행고도에 따른 양력 및 항력을 계산하여 풍동실험 결과와 비교하였다. 비정상문제에서는 이미 정의된 파표면 위를 표면효과익이 날아가는 경계치 문제로 해석하였다. 파장, 파고, 비행고도의 변화에 따른 날개에 작용하는 비정상 동유체력을 계산하여 파가 있을 경우 표면효과의 영향을 살펴보았다.

• 한국군사과학기술학회지
• /
• 제27권3호
• /
• pp.416-427
• /
• 2024

The wake-homing underwater guided weapon that detects and tracks wake generated during voyage of a surface ship is impossible to avoid with the present acoustic deception torpedo defense system. Therefore, research on bubble-generating wake decoy is necessary to deceive wake-homing underwater guided weapon. Experiments in various environments are required to verify the effective operation method and performance of the wake decoy, but performance verification through underwater experiment is limited. In this paper, we develop a simulator for an torpedo defense system of surface ship, which is applied bubble-generating wake decoy, against acoustic, wake, and hybrid homing underwater guided weapon attack. The simulator includes surface ship model, acoustic decoy(static, mobile) model, bubble-generating wake decoy model, search and motion model of underwater guided weapon and so on. By integrating various models, MATLAB GUI simulator was developed. Through the simulation results for various environmental variables by this simulator, it is judged that effective operation method and performance verification of the bubble-generating wake decoy can be performed.

• 한국건축시공학회지
• /
• 제5권3호
• /
• pp.75-82
• /
• 2005

Sewage facilities are positively necessary for environment improvement such as rainwater removal, sewage disposal, preservation of the quality of water and health of the citizens in present-day. Meanwhile, a deterioration of the concrete sewer pipe is increasing rapidly due to the chemical and physical attack and especially biochemical attack that is to say biodeterioration. So, in advanced countries, prediction techniques and corrosion inhibition system for sewer concrete are developed and are being applied. Also, antibiotics were developed already but application of that is low because it is not economical and has no practical use. But, in domestic, countermeasures for the corrosion of sewage concrete are not sufficient and biochemical attack is not reflected in those essentially. In this study, to prevent biochemical corrosion of the sewer concrete, surface of the concrete was spread with liquefied inorganic antibiotics and then its engineering properties were experimentally investigated. As a result, compressive strength of the specimen spread with antibiotics were similar to those of non spread, Both bond strength and abrasion amount of the specimen spread with antibiotics were inferior to non spread. Properties of absorption and air permeability of the specimen spread with antibiotics were superior to non spread. Finally, carbonation depth, chloride ion penetration depth and weight change ration of the specimen spread with antibiotics were smaller than non spread.

• 한국항공우주학회지
• /
• 제36권9호
• /
• pp.825-834
• /
• 2008

고 받음각에서의 방향 안정성 향상을 위한 chine 형상 최적화를 수행하였다. Super ellipse equation을 통하여 다양한 형태의 chine 형상을 생성하고, 3차원 Navier-Stokes 방정식을 이용하여 방향안정성 및 고받음각에서의 공력 특성을 분석하였으며, 가장 높은 방향 안정성을 갖는 형상을 기본형상으로 선정하였다. 파리미터를 이용한 기본형상의 곡면 변형을 통하여 높은 방향 안정성 및 양항비를 동시에 만족하는 최적형상 도출을 위하여, 반응면을 구성하고 가중치를 도입하고 양항비를 구속조건으로 하는 방향안정성 최적화 문제를 수행하였다. 본 연구를 통하여 고받음각에서 chine형상의 공력특성을 파악하여 강한 와류를 발생시키는 chine 형상이 방향안정성에 도움이 된다는 것을 확인할 수 있었으며 최적화를 통해 기본형상보다 방향안정성이 약 29% 향상되는 결과를 얻었다. 또한 파라미터 기반 형상 생성기법과 근사최적화 기법의 연동을 이용한 형상최적설계 과정을 초음속, 고받음각 유동의 chine 형상설계에 적용하여 그 효율성을 확인하였다.

• Wind and Structures
• /
• 제3권3호
• /
• pp.209-220
• /
• 2000

The Strouhal number is an important nondimensional number which is explanatory of aerodynamic instability phenomena. It takes on the different characteristic constant value depending upon the cross-sectional shape of the body being enveloped by the flow. A number of investigations into this subject, especially on the drag test, surface pressure test and hot-wire test, have been carried out under the fixed state of the body in the past. However, almost no investigations concerning the determination of the St on wind-induced vibration of the body have been reported in the past even though the aerodynamic behavior of the body is very important because the construction of wind-sensitive structures is recently on the sharp increase. Based on a series of wind tunnel tests, this paper addresses a new method to determine the Strouhal number of rectangular cylinder in the uniform flow. The central idea of the proposed method is that the Strouhal number can be obtained directly by the aerodynamic behaviors of the body through wind-induced vibration test. The validity of proposed method is evaluated by comparing with the results obtained by previous studies in three B/Ds at attack angle $0^{\circ}$ and a square cylinder with various attack angles. The values and trends of the proposed Strouhal numbers are in good agreements with values of previous studies. And also, the Strouhal numbers of B/D=1.5 and 2.0 with various attack angles are obtained by the proposed method and verified by other method. This proposed method is as good as any other previous methods to obtain the Strouhal number.

• 한국항해항만학회지
• /
• 제32권10호
• /
• pp.771-776
• /
• 2008

선박에서 제어판의 역할은 운동을 제어하는데 목적이 있으며 이는 곧 조종성능을 결정하는 중요한 요소이다. 본 연구에서는 플랩타의 성능평가를 위하여 $Re=3.0{\times}10^4$에서 영각에 대응하는 플랩각에 따른 속도 및 에너지 분포를 2-프레임 그레이레벨 상호상관 PIV기법을 이용하여 비교 분석하였다. 또한 영각 10도와 20도에서 전통적인 단동타의 유동특성과 비교하여 플랩타의 성능특성을 평가하였다. 영각 10도에서는 양력, 영각 20도에서는 항력에 의한 측압력을 향상시킬 수 있었다. 영각 10도에서 플랩조작만으로 박리점과 경계층영역의 변화가 가능하였다.

• 콘크리트학회논문집
• /
• 제28권2호
• /
• pp.149-156
• /
• 2016

염해에 노출된 콘크리트의 내구수명은 매우 중요한데, 주로 Fick's 2법칙에 근거한 결정론적인 방법과 확률론에 근거한 방법이 사용되고 있다. 본 연구에서는 시간의존적 확산계수와 표면염화물량을 고려하여 내구적 파괴확률과 이에 따른 내구수명의 변화를 평가하였다. 이를 위해 3.5~4.5년, 비교적 짧은 기간 염해에 노출된 RC 교각에 대하여 해상부(9.0 m)와 간만대(6.0 m) 구분하여 실태조사를 수행하였다. 피복두께, 표명염화물량, 염화물 확산계수에 대한 확률변수를 도출하였으며, MCS을 이용하여 내구적 파괴확률과 내구수명을 평가하였다. Life365를 이용한 결정론적 방법과 다르게, 시간의존성을 고려한 확률해석에서는 내구수명의 변동이 크게 발생하였으며, 표면염화물량이 낮은 조건에서는 초기에 빠른 내구수명의 감소가 평가되었다. 실태조사 결과를 이용하여 확률론적인 내구성 평가를 할 경우, 장기간 염해에 노출되어 $10.0kg/m^3$ 이상의 높은 표면염화물량이 필요함을 알 수 있으며, 확산계수의 시간의존성에 따른 감소를 고려하면 합리적인 내구수명을 평가할 수 있다.

• Advances in aircraft and spacecraft science
• /
• 제4권1호
• /
• pp.37-52
• /
• 2017

Gas turbines operating in dusty or sandy environment polluted with micron-sized solid particles are highly prone to blade surface erosion damage in compressor stages and molten sand attack in the hot-sections of turbine stages. Commercial/Military fixed-wing aircraft engines and helicopter engines often have to operate over sandy terrains in the middle eastern countries or in volcanic zones; on the other hand gas turbines in marine applications are subjected to salt spray, while the coal-burning industrial power generation turbines are subjected to fly-ash. The presence of solid particles in the working fluid medium has an adverse effect on the durability of these engines as well as performance. Typical turbine blade damages include blade coating wear, sand glazing, Calcia-Magnesia-Alumina-Silicate (CMAS) attack, oxidation, plugged cooling holes, all of which can cause rapid performance deterioration including loss of aircraft. The focus of this research work is to simulate particle-surface kinetic interaction on typical turbomachinery material targets using non-linear dynamic impact analysis. The objective of this research is to understand the interfacial kinetic behaviors that can provide insights into the physics of particle interactions and to enable leap ahead technologies in material choices and to develop sand-phobic thermal barrier coatings for turbine blades. This paper outlines the research efforts at the U.S Army Research Laboratory to come up with novel turbine blade multifunctional protective coatings that are sand-phobic, sand impact wear resistant, as well as have very low thermal conductivity for improved performance of future gas turbine engines. The research scope includes development of protective coatings for both nickel-based super alloys and ceramic matrix composites.