• Journal of computational fluids engineering
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• v.15 no.4
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• pp.85-91
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• 2010

In this study, aerodynamic analyses based on unsteady computational fluid dynamics (CFD) have been conducted for a 2-bladed vertical-axis wind turbine (VAWT) configuration. Reynolds-averaged Navier-Stokes equations with standard $k-{\varepsilon}$ and SST $k-{\varepsilon}$ turbulence models are solved for unsteady flow problems. The experiment model of 2-bladed VAWT has been designed and tested in this study. Aerodynamic experiment of the present VAWT model are effectively conducted using the vehicle mounted testing system. The comparison result between the experiment and the computational fluid dynamics (CFD) analysis are presented in order to verify the accuracy of CFD modeling with different turbulent models.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.723-728
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• 2001

Wind flow perturbations, recirculations and turbulence generated by buildings often dominate air pollutant distributions around buildings. This paper describes dispersion of contaminants in the vicinity of a building by solving the concentration equation based on previously simulated wind flow field. Turbulence closure is achieved by using the standard k-e two-equation model. The paper shows application of the CIP method for solving a species concentration equation of contaminant gas around a rectangular building for two different sources under conditions of neutral atmospheric stratification. Results have been compared to the experimental data and the previous numerical results by hybrid scheme. The computational results of concentration profiles by the CIP method agree well with experimental data.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.568-573
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• 2000

In this study, experimental and numerical analyses are carried out to investigate the performance of centrifugal pump with various air admitting conditions. Experiments on pump performance under air-water two-phase flow n accomplished using a centrifugal pump with semi-open type impeller having three, five and seven blades, respectively. Also, the numerical analysis of turbulent air-water two-phase flow using finite volume method has been carried out to obtain the pressure, velocities and void fraction on the basis of a so-called bubbly flow model with the constant size and shape of cavity. The results obtained through this study show the reasonable agreements within the range of bubbly flow regime. There are promising developments concerning application of the present study for the flow in a centrifugal pump with two-phase flow conditions and efforts must be followed to improve the turbulence model and two-phase flow model for turbomachinery.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.479-484
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• 2000

A Navier-stokes based finite volume method has been developed to analyze an incompressible, steady state, turbulent wall-jet flow. The standard k-e model, the RNG ${\kappa}-{\varepsilon}$ model and their nonlinear counterparts are adopted as a closure relationship. Comparison with the experimental data shows that a linear ${\kappa}-{\varepsilon}$ model performs satisfatorily for two-dimensional wall-jet flows. However, as the flow becomes three dimensional, the linear model fails to predict the spanwise jet growth accurately and the nonlinear model needs to be adopted to capture three-dimensional flow characteristics.

• Journal of Power System Engineering
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• v.9 no.4
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• pp.31-38
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• 2005

육상 수조식 양식장은 해수를 끌어들여 어류를 기르는 데 사용된다. 본 연구는 사각 수조 내의 다양한 기하학적 관계와 유동에 대한 유동 특성을 도출하였다. 수치해석은 유한 체적법과 SIMPLE 기수법은 수치해석법을 활용하였으며, 비압축성 유체와 3차원 표준 $k-{\varepsilon}$난류 모델을 적용하였다. 속도 분포, 온도 분포에 대한 정보를 확보하였다. 실험과 수치해석의 결과가 정성적으로 잘 일치함을 보였다. 양식장의 깊이가 증가함에 따라 바닥 쪽의 유동이 더욱 안정됨을 확인하였다. 이는 각종 배설물 등의 정체현상으로 연결될 수 있음을 확인하였다. 수조내의 온도는 유입구의 초기 온도가 중요하며, Re 수가 증가할수록 온도는 상승하고 유입구의 반대 벽면 근처의 온도가 유입구 보다 증가함을 알 수 있었다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.2
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• pp.91-98
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• 1993

A two-dimensional turbulence model for the surface discharge of heated water into cross-flow field has been developed. The depth-averaged continuity, momentum and temperature equations, are solved by an efficient finite-difference procedure known as SIMPLE. Turbulent stresses and heat fluxes are determined from a depth-averaged version of the $textsc{k}$-$\varepsilon$ equation. Results of test run clearly demonstrate its effectiveness in handling strong turbulent phenomena in very shallow near-field region.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.301-304
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• 2001

Hot-compression tests were carried out to investigate the hot workability of Ti64 and Ti6246 alloys at different temperatures and strain rates. Processing maps were developed on the basis of the dynamic material model unifying the relationship among constitutive behavior, hot workability and microstructure development. Stable regions, defined on the basis of four stability criteria 0${\delta}log(m)/\frac{\bot}{\varepsilon})<0$, s<1 and ${\delta}log(s)/\frac{\bot}{\varepsilon})<0$, were found to be associated with dynamic recovery and recrystallization.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.1
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• pp.184-192
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• 1994

The parameters such as Richardson numbers or stability parameters are widely used to account for the extra straining effects due to three-dimensionality, curvature, rotation, swirl and others arising in paractical complex flows. Existing expressions for the extra strain in turbulence models such as $k-{\epsilon}$ models, however, do not satisfy the tensor invariant condition representing the coordinate indifference. In the present paper, considering the characteristics of both the mean strain rate and the mean vorticity, a new parameter to deal with the extra straining effects is proposed. The new parameter has a simple form and satisfies the tensor invariant condition. A semi-quantitative analysis between the present and previous parameters for several typical complex flows suggests that the newly proposed parameter is more general and adequate in representing the extra straining effects than the previous ad-hoc parameters.

• Journal of Korean Philosophical Society
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• v.126
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• pp.263-293
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• 2013

Die vorliegende Abhandlung beachtet die methodologische $N{\ddot{u}}tzlichkeit$ der Dialektik $f{\ddot{u}}r$ die philosophische $Wissenschaftst{\ddot{a}}tigkeit$ des Aristoteles in einer besonderen Aufmerksamkeit auf den Begriff "${\delta}{\iota}{\alpha}{\pi}o{\rho}{\varepsilon}{\iota}{\nu}$". Bei Aristoteles bedeutet "${\delta}{\iota}{\alpha}{\pi}o{\rho}{\varepsilon}{\iota}{\nu}$" 'das durchaus $gr{\ddot{u}}ndliche$ Untersuchen einer Aporie', und eine solche Untersuchungsweise folgt der Dialektik. Deshalb beabsichtige ich zuerst, durch eine Begriffsanalyse und - interpretation von "${\delta}{\iota}{\alpha}{\pi}o{\rho}{\varepsilon}{\iota}{\nu}$" die dialektische Aporetik zu bestimmen als eine Argumentationsmethode nicht nur in einer dialogischen, sondern auch in einer nicht-dialogischen Situation. Besonders will ich einen methodologischen Grund $daf{\ddot{u}}r$ suchen, dass ein allein Forschender in der nicht-dialogischen Situation die dialektische Aporetik verwendet, indem ich einen Text von "De caelo" II 13, 294b 6~13 interpretiere. $N{\ddot{a}}mlich$ betont Aristoteles in Bezug auf den Durchgang der $Wissenschaftst{\ddot{a}}tigkeit$ eine Forderung der selbstkritischen Haltung, die der allein Forschende sich selbst seine Untersuchung in $R{\ddot{u}}cksicht$ auf die anderen Untersuchungen und auch auf die vorhersehbaren Hypothesen ${\ddot{u}}berpr{\ddot{u}}fen$ und verifizieren, um die aus seiner Untersuchung zu entdeckenden Aporien auf die dialektische Weise zu $l{\ddot{o}}sen$. Und diese Position von Aristoteles kann der wichtige Grund $daf{\ddot{u}}r$ sein, den fachsprachlichen Sinn von "${\delta}{\iota}{\alpha}{\pi}o{\rho}{\varepsilon}{\iota}{\nu}$" als auch den wissenschaftlichen Sinn der dialektischen Untersuchung der Aporie richtig verstehen und $erkl{\ddot{a}}ren$ zu $k{\ddot{o}}nnen$. Zuletzt bin ich in der Absicht, die dialektische Aporetik und ihre Funktion in drei Modeln zu formulieren und einige Beispiele $f{\ddot{u}}r$ jedes Model vorzustellen, um zu zeigen, auf welche Art und Weise Aristoteles die dialektische Aporetik $f{\ddot{u}}r$ den Lauf seiner Theoriebildung in der Tat anwendet. Durch solchen Versuch $w{\ddot{u}}nsche$ ich, dass meine Untersuchung ${\ddot{u}}ber$ die dialektische Aporetik etwas besseres $Verst{\ddot{a}}ndnis$ $f{\ddot{u}}r$ die wissenschaftliche Bedeutung der aristotelischen Dialektik anbieten $k{\ddot{o}}nnte$, und auch dass diese Studie als bedeutsame Basisdaten zu einer noch tieferen Forschung und $Verst{\ddot{a}}ndigung$ ${\ddot{u}}ber$ die philosophische Haltung und Methode des Aristoteles betrachtet werden $k{\ddot{o}}nnte$.

• Journal of the Korean earth science society
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• v.22 no.1
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• pp.1-9
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• 2001

Composition of the major and trace elements, Rb-Sr isochron age Sr-Nd isotope composition were determined for foliated in the Jeonju area, in the middle part of the Ogcheon Fold Bet, Korea. The geochemical characteristics of the Jeonju foliated granite indicate that the granite had been crystallized from a calc-alkaline series, and formed in a volcanic are environment. The isotopic compositions of the Jeonju foliated granite give Rb-Sr whole rock errorchron age of 168.2${\pm}$8 Ma(2${\sigma}$), corresponding to the middle Jurassic period, with the Sr initial ratio of 0.71354${\pm}$0.00031. $^{143}$Nd/$^{144}$Nd ratios, ${\varepsilon}$Nd and ${\varepsilon}$Sr values range from 0.511477 to 0.511744, -15.4${\sim}$-21.2, and +108.8${\sim}$+l42.6, respectively. Model ages were caculated to be 1.82${\sim}$2.89Ga. The isotopic data of Jeonju foliated granite indicate that the source material may have been derived from partial melting of continental crust materials.