비정렬 유한 체적법을 이용한 횡류 홴 유동장 해석

강동진,배상수,Kang Dong-Jin,Bae Sang-Su 한국유체기계학회 2006 한국유체기계학회 논문집 Vol.9 No.4

A Navier-Stokes code has been developed to simulate the flow through a cross flow fan. It is based on an unstructured finite volume method and uses moving grid technique to model the rotation of the fan. A low Reynolds number turbulence model is used to calculate eddy viscosity. The basic algorithm is SIMPLE. Numerical simulations over a wide range of flow rate are carried out to validate the code. Comparison of all numerical solutions with experimental data confirms the validity of the present code. Present numerical solutions show a noticeable improvement over a previous numerical method which is based on a model of body force to simulate the rotation of the impeller.

정익과 동익의 상호작용에 의한 비정상 천이 경계층 유동의 수치해석에 관한 연구 1

강동진,Kang, Dong-Jin,Lakshminarayana, Budugur 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.6

A Navier-Stokes code with a low Reynolds number k-.epsilon. turbulence model was tested to investigate its predictability for the unsteady transitional boundary layer flow due to rotor-stator interaction. A preliminary calculation with three different numbers of time steps 300, 600, and 1000 for a rotor wake passing period was carried out to see the effects of time steps on the unsteady flow and pressure fields due to rotor-stator interaction. Numerical solutions showed that unsteady pressure was much more sensitive to the number of time steps and over 600 time steps should be used to get a numerical solution independent of the number of time steps for a rotor wake passing period. The original low Reynolds number k-.epsilon. turbulence model showed very poor prediction of the unsteady transitional boundary layer flow due to rotor-stator interaction. This was due to the excessive production of turbulent kinetic energy near the leading edge. A modification suggested by Launder was incorporated and the modified model captured well the wake induced transitional strip. Present solutions also showed improved prediction over previous Euler/boundary layer solution in terms of the onset of unsteady transition and its extent.

비정렬 유한체적법을 위한 QUICK법의 수정

강동진,배상수,Kang, Dong Jin,Bae, Sang Soo 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.9

The QUICK scheme for convection terms is modified for unstructured finite volume method by using linear reconstruction technique and validated through the computation of two well defined laminar flows. It uses two upstream grid points and one downstream grid point in approximating the convection terms. The most upstream grid point is generated by considering both the direction of flow and local grid line. Its value is calculated from surrounding grid points by using a linear construction method. Numerical error by the modified QUICK scheme is shown to decrease about 2.5 times faster than first order upwind scheme as grid size decreases. Computations are also carried out to see effects of the skewness and irregularity of grid on numerical solution. All numerical solutions show that the modified QUICK scheme is insensitive to both the skewness and irregularity of grid in terms of the accuracy of solution.

MIT 요동 익형의 수치해석

강동진,배상수,Kang, Dong-Jin,Bae, Sang-Soo 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.6

A Navier-Stokes code based on an unstructured finite volume method is used to simulate the MIT flapping foil experiment. A low Reynolds number ${\kappa}-{\varepsilon}$ turbulence model is used to close the Reynolds averaged Navier-Stokes equations. Computations are carried out for the whole experimental domain involving two flapping foils and a downstream hydrofoil. The computational domain is meshed with unstructured quadrilateral elements, partly structured. Numerical solutions show good agreement with experiment. The first harmonics of the velocity in the boundary layer shows local peak value inside the boundary layer and also local minimum near the edge of boundary layer. It is intensified as it develops along the blade surface. This is shown to be caused as the unsteadiness inside the boundary layer is being convected at a speed less than the free stream value. It is also shown that there is negligible mixing of the unsteadiness between the boundary layer and the free stream.

1990/91년 남극하계 브렌스필드 해협 표층해수의 $\delta$/SUP 18/O와 영양염 분포

강동진,정창수,리쿠퍼,강천윤,김예동,홍기훈,KANG, DONG-JIN,CHUNG, CHANG SOO,COOPER, LEE W.,KANG, CHEONG YOON,KIM, YEA DONG,HONG, GI HOON The Korean Society of Oceanography 1992 韓國海洋學會誌 Vol.27 No.3

The oxygen isotope composition of surface waters in the Bransfield Strait was determined as one extra state variable in order to characterize water masses in the region, since salinity is significantly modified due to the freezing and ice-melting in the polar region. The salinity, temperature, and $\delta$/SUP 18/O values vary from 34.0 to 34.5$\textperthousand$, -.05 to 2.1$^{\circ}C$ and -0.50 t -0.26$\textperthousand$, respectively. The combined effects of evaporation, precipitation, freezing, ice-melting are reflected in the widely scattered data. Although it is small, the distribution of $\delta$/SUP 18/O of the Bransfield Strait is strongly affected by the freezing-ice melting rather than the evaporation-precipitation. The ice melted fresh water which has higher temperature, depleted salinity and nutrients may be injected to the Bransfield Strait from the north. The concentrations of nutrients are decreasing gradually from the north to the south. The waters were characterized by two groups of higher (about 19.4) and lower N/P ratio (about 16.7). The lower N/P ratio is found in the northern part where ice-melted fresh water is injected. and the higher N/P ratio is found in the southern part of the Bransfield Strait. Although more precise work is needed, the deference of N/P ratio can be an evidence of the ice melted water injection to the Bransfield Strait. Chlorophyll a concentrations, in general, increase from northwest (Waddell Sea) to the southeast (Smith and Hosseason Islands). Probably the injection of nutrient depleted fresh water from the ice melting reduce the chlorophyll a concentration.

가스터빈 기관의 탈설계점 해석

강동진,류제욱,정평석,Kang, D.J.,Ryu, J.W.,Jung, P.S. 대한기계학회 1993 대한기계학회논문집 Vol.17 No.7

A procedure for the prediction of the off-design performance of a gas turbine engine is proposed. The system performance at off-design speed is predicted by coupling the thermodynamic models of a compressor and a turbine. The off-design performance of a compressor is obtained using the stage-stackimg method, while the Ainlay-Mathieson method is used for a turbine. The procedure is applied to a single-shaft gas turbine and its predictability is found satisfactory. The results also show that the net work output increases with the increase of the turbine inlet temperature, while the thermal efficiency is marginal. The maximum thermal efficiency at design point is obtained between the highest pressure ratio and design pressure ratio.

병렬 컴퓨터에서 다중블록 유한체적법을 이용한 비압축성 유동해석

강동진,손정락,Kang, Dong-Jin,Sohn, Jeong-Lak 한국유체기계학회 1998 한국유체기계학회 논문집 Vol.1 No.1

Computational analysis of incompressible flows by numerically solving Navier-Stokes equations using multi-block finite volume method is conducted on a parallel computing system. Numerical algorithms adopted in this study $include^{(1)}$ QUICK upwinding scheme for convective $terms,^{(2)}$ central differencing for other terms $and^{(3)}$ the second-order Euler differencing for time-marching procedure. Structured grids are used on the body-fitted coordinate with multi-block concept which uses overlaid grids on the block-interfacing boundaries. Computational code is parallelized on the MPI environment. Numerical accuracy of the computational method is verified by solving a benchmark test case of the flow inside two-dimensional rectangular cavity. Computation in the axial compressor cascade is conducted by using 4 PE's md, as results, no numerical instabilities are observed and it is expected that the present computational method can be applied to the turbomachinery flow problems without major difficulties.

On Board Comparison of Total Hydrogen Ion Concentration (pH) and Total Alkalinity Measurements in Seawater

강동진,티쉬첸코 파벨,강성현,Kang, Dong-Jin,Tishchenko, Pavel Ya,Kahng, Sung-Hyun The Korean Society for Marine Environment and Ener 2011 한국해양환경·에너지학회지 Vol.18 No.4

해수 중의 수소이온농도(pH)와 총알칼리도(TA) 측정 방법에 대한 선상 비교 연구가 동해 표층에서 저층에 이르는 약 550개의 실제 해수 시료에 대해 이루어졌다. 분광광도법과 전위차법에 대한 pH의 비교가 이루어졌으며, 두 방법에 의한 해수의 pH는 전반적으로 잘 일치하였으나, pH가 낮은 심층의 경우 피펫을 사용한 분광법에 의한 값이 전위차법 보다 높은 값을 보였다. 그러나 피펫을 사용하지 않은 분광법과는 두 방법의 정밀도 내에서 동일한 값을 보였다. 이는 피펫에 의해 해수 내의 이산화탄소가 제거되면서 시료 내의 pH를 증가시키는 것으로 판단된다. TA 측정법의 비교를 위해 폐쇄 용기를 이용한 전위차법과 개방 용기를 이용한 전위차법이 사용되었으며, 개방형 용기를 사용했을 때의 값이 폐쇄형 용기를 사용했을 때의 값에 비해 약 5~10 ${\mu}mol\;kg^{-1}$ 작은 값을 보인다. 이는 폐쇄형 용기를 사용했을 때, 적정 도중에 발생하는 이산화탄소가 용액 속에 남아 적정액인 염산 이외의 산을 용액 속에 추가하는 효과를 내기 때문으로 판단된다. 따라서 pH혹은 TA의 분석에 있어서 본 연구에서 비교한 어느 방법을 사용할 수도 있지만 각각의 방법에 대해 특별히 요구되는 주의를 기울일 때 만족할 만한 분석결과를 얻을 수 있다. On board comparison of pH and total alkalinity measurement in seawater was carried out during the JES expedition on R/V Roger Revelle in the East Sea using 550 real seawater samples from the surface to the bottom. Spectrophotometry and potentiometry without liquid junction were compared for pH measurement. The pH values of two methods are generally in a good agreement. Spectrophotometry with a pipette provides higher value compare with the potentiometry in the deep layer, where pH values are lower. However, spectrophotometry without a pipette shows same values with potentiometry within their precision range. The pipetting procedure may remove of $CO_2$ in the sample, which causes increase of pH. Potentiometric titration methods using a closed-cell and an open-cell were compared for the total alkalinity measurement. Values from open cell method are smaller by about 5~10 ${\mu}mol\;kg^{-1}$ than those from closed cell method. This may be caused by the bubble formed in the closed cell during the experiment. Although any analytical method compared in this study for the pH or TA measurement can be applied, special attentions should be paid for satisfactory results.

연속된 정수의 멱의 합의 변천사에 대한 고찰

강동진,김대열,박달원,서종진,임석훈,장이채,Kang Dong-Jin,Kim Dae-Yeoul,Park Dal-Won,Seo Jong-Jin,Rim Seog-Hoo,Jang Lee-Chae 한국수학사학회 2006 Journal for history of mathematics Vol.19 No.1

In 1713, J. Bernoulli first discovered the method which one can produce those formulae for the sum $\sum\limits_{\iota=1}^{n}\;\iota^k$ for any natural numbers k ([5],[6]). In this paper, we investigate for the historical background and motivation of the sums of powers of consecutive integers due to J. Bernoulli. Finally, we introduce and discuss for the subjects which are studying related to these areas in the recent. 수학에서 가장 매력적이고 중요한 이론들 중에 하나로 알려진 베르누이 (Bernoulli)수의 변천과정을 고찰한다. 즉, 당시대의 이러한 연속된 정수의 멱의 합에 대한 수학사적 배경들을 조사하고, 베르누이 수와 관련된 연구들이 현재 어떠한 방향으로 진행되고 있는지를 살펴본다.

산업유산으로서의 폐광산 재활용 방법론 연구

강동진,Kang, Dong-Jin 한국조경학회 2007 韓國造景學會誌 Vol.34 No.6

Industrial heritage artifacts may include the industrial products, technologies and infrastructures that have contributed to modernization beginning with the Industrial Revolution. The history of our industrial heritage spans 50 to 150 years and can be characterized by taking into account the site and the technology. This paper analyzes 13 precedents in Japan, Canada, and the United States in terms of these concerns, with focus on the reuse of abandoned mines as industrial heritage. Field surveys and interviews about each abandoned mine were used to obtain historical records and material. The results describe progress in three phases (1) recognizing phase, (2) organizing phase, and (3) maintenance management phase. A proper methodology for reuse is necessary to ensure the authenticity of the abandoned mine, particularly in the face of poor tourism-oriented approaches. As a result of analyzing the 13 cases, we determined that the following principles should be considered during the reuse process. Firstly, reuse of abandoned mines should not be compulsory but should be a spontaneous process and especially, should be carried out by inhabitants. Secondly, education and real experiences in the abandoned mine should be used to ive visitors a feeling of authenticity. Thirdly, creative remodeling methods can be used to enhance the abandoned mine's facilities and the site. Finally, historic and new functions should be the focus of the revitalization. Because this paper mainly focused on 13 precedents, there are likely more diverse cases. However, the conclusions of this report have practical value for reuse of abandoned mines and can be used in establishing methods for reusing Korean abandoned mines as industrial heritage.