• Journal of the Society of Naval Architects of Korea
• /
• v.43 no.6 s.150
• /
• pp.675-682
• /
• 2006

This study has investigated the turbulent flow around a square cylinder by using LES (large eddy simulation). Numerical simulations are performed for turbulent flow fields with Re = 22,000. The computed results are in good agreement with existing computational and experimental data. The time-averaged and phase-averaged turbulent statistics around a square cylinder are discussed. Total 20 phase bins extracted from one cycle period showed detailed wake structures of the phase-averaged flow field. The center of Karman vortex sheets did not deviated ${\pm}0.5$ from centerline of square cylinder while moving downstream.

• Proceeding of EDISON Challenge
• /
• 2013.04a
• /
• pp.321-326
• /
• 2013

본 연구에서는 원형실린더의 강제 수평 및 수직진동에 따른 와흘림을 관찰하였다. EDISON_CFD의 가상경계법을 이용하여 원형실린더 주위 유동현상을 수치 모사하였다. 원형실린더의 강제 진동 특성에 따른 와흘림 진동수, 공력계수 등의 영향을 분석하였다. 특히, 진동방향에 따른 와흘림의 영향을 분석하여, 원형실린더의 강제 진동에 따른 유동의 선형성을 평가하였다.

• Journal of Ocean Engineering and Technology
• /
• v.20 no.4 s.71
• /
• pp.76-82
• /
• 2006

The large-eddy simulation(LES) technique, based an a message passing interface method(MPI), was applied to investigate the turbulent flaw phenomena around a ship. The Smagorinski model was used in the present LES simulation to simulate the turbulent flaw around a ship. The SPMD(sidsngle program multiple data) technique was used for parallelization of the program using MPI. All computations were performed an a 24-node PC cluster parallel machine, composed of 2.6 GHz CPU, which had been installed in the Advanced Ship Engineering Research Center(ASERC). Numerical simulations were performed for the Wigley hull, and the Series 60 hull(CB=0.6) using 1/4-, 1/2-, 1- and 2-million grid systems and the computational results had been compared to the experimental ones.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 1999.05a
• /
• pp.2-2
• /
• 1999

금속재료의 표면 특성을 높이기 위해서 여러 표면처리 방법들이 사용되어져 오고 있다. 그 중 용사법에 의한 코팅방법이 최근의 현저한 기술적인 진보와 새로운 용사재료의 개발 등에 의해 여러 분야에 널리 응흉되고 있다. 일반적으로 이 용사법에 의한 코팅층은 다리, 선박 등의 대형 구조물에 대한 내식성 향상뿐만 아니라 자동차 및 항공기 부품, 핵 반응기 등의 코팅부에 널리 이용되고 였다. 특히 해수분위기에서 주로 사용되는 설비의 내식성을 향상시킬 목적으로 사용되 는 알루마늄 및 아연 합금의 용사 코팅층은 대부분의 경우 건조한 분위기보다는 수분이 많은 수용액 환경 하에서 사용되므로, 사용 환경 중에서 용사피막의 내식성을 조사하는 연구가 요구되고 있다. 사용되는 환경하에서의 침지시험에 의한 방법도 중요하지만, 가속화된 전기화학측정에 의한 방법 또한 이용된다. 열용사법에 의한 코팅층의 전기화학적 특성을 알아보기 위해서 3.5 % NaCI 수용액 내에서 AI 5 5083 모재와 Al-2%Zn 합금의 용사 코팅층 각각에 대한, 그리고 AI 5083 모재 위 AI-2%Zn 용사층이 코팅된 경우에 대한 분극거동과 침지시간에 따른 부식전위 및 분극저항성의 특성변화, 표면의 임피던스특성 변화 등을 측정하였다. 이 결과 모재에 대한 코팅층의 희생양극성올 판단할 수 있고, 모재/코팅 사스템의 분극거동은 혼성전위이론(mixed-potential theory)에 의해 결정되었다. 용사 코팅층이 박리되어 모재가 일부 드러난 경우를 모사한 시험편올 제작하고, 시험편 표면의 각 위치에 따라 부식전위 분포를 측정하였다. 그리고 측정 데이터를 기초로 표면의 상태변화를 모사하여 용사코팅에 의한 표면에서의 방식전위분포를 시율레이션하였다. 이와 같은 표면에서의 방식전위분포 해석을 통하여, 코팅층의 희생양극성에 의한 모재의 방식범위를 판단할 수 있다.의 비저 항을 갖는 철 박막에서도 99.9% 순도의 철을 타켓으로 하여 증착된 막은 일반 저탄소 강을 타켓으로 하여 증착된 막보다 훨씬 낮은 부식속도를 보였다.TEX>$He/O_2/Ar/N_2$의 gas를 사용 한 atmospheric pressure plasma cleaning 과 $Ar/O_2$의 gas를 사용한 ICP cleaning에서 이 차전자방출계수(SEEC)가 약 1.5~2.5배 증가된 것을 알 수 있었다. 저지능 등을 평가하여 각 실험결과를 비교분석하여 보았다. 수록 민감하여 304 의 IGSCC 와 매우 유사한 거동을 보인다. 본 강연에서는 304 와 600 의 고온 물에서 일어나는 IGSCC 민감도에 미치는 환경, 예민화처리, 합금원소의 영향을 고찰하고 이에 대한 최근의 연구 동향과 방식 방법을 다룬다.다.의 목적과 지식)보다 미학적 경험에 주는 영향이 큰 것으로 나타났으며, 모든 사람들에게 비슷한 미학적 경험을 발생시키는 것 이 밝혀졌다. 다시 말하면 모든 사람들은 그들의 문화적인 국적과 사회적 인 직업의 차이, 목적의 차이, 또한 환경의 의미의 차이에 상관없이 아름다 운 경관(High-beauty landscape)을 주거지나 나들이 장소로서 선호했으며, 아름답다고 평가했다. 반면에, 사람들이 갖고 있는 문화의 차이, 직업의 차 이, 목적의 차이, 그리고 환경의 의미의 차이에 따라 경관의 미학적 평가가 달라진 것으로 나타났다.corner$적 의도에 의한 경관구성의 일면을 확인할수 있지만 엄밀히 생각하여 보면 이러한 예의 경우도 최락의 총체적인 외형은 마찬가지로 $\ulcorner$순응$\lrcorner$의 범위를 벗어나지 않는다. 그렇기 때문에도 $\ulcorner$순응$\lrcorne

• Journal of the Korean Geotechnical Society
• /
• v.28 no.8
• /
• pp.5-19
• /
• 2012

Vertical drains along with the preloading technique have been commonly used to enhance the consolidation rate of dredged placement formation. In practice, vertical drains are usually installed in the process of self-weight consolidation of a dredged soil deposit because this process takes considerable time to be completed, which makes conventional analytical or numerical models difficult to quantify the consolidation behavior. In this paper, we propose a governing partial differential equation and develop a numerical model for 2-D axisymmetric non-linear finite strain consolidation considering self-weight consolidation to predict the behavior of a vertical drain in the dredged placement foundation which is installed during the self-weight consolidation. In order to verify the developed model in this paper, results of the numerical analysis are compared with that of the lab-scaled self-weight consolidation test. In addition, the model verification has been carried out by comparing with the simplified method. The comparisons show that the developed model can properly simulate the consolidation of the dredged placement formation with the vertical drains installed during the self-weight consolidation. Finally, the effect of construction schedule of vertical drains and of pre-loading during the self-weight consolidation is examined by simulating an imaginary dredged material placement site with a thickness of 10 m and 20 m, respectively. This simulation infers the applicability of the proposed method in this research for designing a soil improvement in a soft dredged deposit when vertical drains and pre-loading are implemented before the self-weight consolidation ceases.

• Economic and Environmental Geology
• /
• v.41 no.2
• /
• pp.201-210
• /
• 2008

The mixing treatment process using lime (CaO) and limestone ($CaCO_3$) as the immobilization amendments was applied for heavy metal contaminated filmland soils around Goro abandoned Zn-mine, Korea in the batch and pilot scale continuous column experiments. For the batch experiments, with the addition of 0.5 wt.% commercialized lime or limestone, leaching concentrations of As, Cd, Pb, and Zn from the contaminated filmland soil decreased by 70, 77, 94, and 95 %, respectively, compared to those without amendments. For the continuous pilot scale column experiments, the acryl column (30 cm in length and 20 cm in diameter) was designed and granulated lime and limestone were used. From the results of column experiments, with only 2 wt.% of granulated lime, As, Cd, and Zn leaching concentrations decreased by 63%, 97%, and 98%, respectively. With 2 wt.% of granulated limestone, As leaching concentration reduced from 135.6 to 30.2 ${\mu}g/L$ within 5 months and maintained mostly below 10 ${\mu}g/L$, representing that more than 46% diminution of leaching concentration compared to that without the amendment mixing. For Cd and Zn, their leaching concentrations with only 2 wt.% of limestone mixing decreased by 97%, respectively compared to that without amendment mixing, suggesting that the capability of limestone to immobilize heavy metals in the filmland soil was outstanding and similar to that of lime. From the column experiments, it was investigated that if the efficiency of limestone to immobilize heavy metals from the soil was similar to that of lime, the limestone could be more available to immobilize heavy metals from the soil than lime because of low pH increase and thus less harmful side effect.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.9
• /
• pp.5877-5884
• /
• 2014

Recently, abnormally cold weather has been reported more frequently in winter due to the climate change and abnormal weather changes. On the other hand, the heating capacity of a railcar may be not enough to warm the cabin under severe cold climatic conditions, which is one of the reasons for the passengers' complaints about heating. In this study, the effects of ambient temperature and heater power on the cabin temperature was investigated to obtain the minimum ambient temperature for the tested railcar. The test railcar was placed in a large-climatic chamber, and various ambient temperature conditions were simulated. The effects of the heater output were investigated by monitoring the cabin temperature under a range of heater output conditions. The mean cabin temperature was $14.0^{\circ}C$, which was far lower than the required minimum temperature of $18^{\circ}C$, under a $-10^{\circ}C$ ambient temperature condition with the maximum heat power. When the ambient temperature was set to $0^{\circ}C$ and $10^{\circ}C$, the maximum achievable cabin temperature was $26.1^{\circ}C$ and $34.0^{\circ}C$. Through calculations using the interpolation method, the minimum ambient temperature to maintain an $18^{\circ}C$ cabin temperature was $-6.7^{\circ}C$ for this car. The vertical temperature difference was higher with a higher power output and higher ambient temperature. The maximum vertical temperature difference was higher than $10^{\circ}C$ in some cases. However, the horizontal temperature difference vs. low temperature (< $2^{\circ}C$) was independent of the power output and ambient temperature. As a result, it is very important to reduce the vertical temperature difference to achieve good heating performance.