• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1495-1499
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• 2010

최근에 기후변화 영향 분석을 위한 강수모의발생 기법에 대한 연구가 중요한 문제로 대두되고 있다. 기본적으로 모의된 강수량이 유역단위에서 의미 있는 값으로 수문모형에 입력자료로 활용되기 위해서는 강수지점간의 공간상관성의 유지가 매우 중요하다. 즉 지역적인 수문학적 거동을 유역단위에서 평가하기 위해서는 유역상관성을 고려할 수 있는 다지점(multisite) 모형의 개발이 필수적이다. 이러한 점에서 본 연구에서는 다지점 강수모의기법을 개발하였으며 비정상성 해석이 가능하도록 동역학적 강수모형을 구성하였다. 이를 한강유역 강수지점에 적용하여 모형의 적합성을 평가하였다.

• The KSFM Journal of Fluid Machinery
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• v.18 no.1
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• pp.44-50
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• 2015

Labyrinth seals are commonly used in various kinds of turbomachinery to reduce leakage flow. In the present 3D CFD analysis of see-through-type labyrinth air seal, the methodology of determining leakage and rotordynamic coefficients is suggested with the relative coordinate system for steady-state simulation. The leakage flow and rotordynamic forces predicted by using different solvers and turbulent models of FLUENT are compared with the results of the existing bulk-flow analysis code LABYSEAL.FOR and experiment. The present CFD result of direct stiffness(K) shows only improvement in prediction. The results of leakage and rotordynamic coefficients as well as computing time are sensitive against the used solver and turbulent model.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.217-221
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• 2016

In this paper, a springboard for diving is analysed to find out how much force a diver should apply to reach specific height when the diver jumps. The springboard is presumed to Co-rotational plane cantilever beam(CR-beam), so EDISON program related to Co-rotational framework is used. The force of the person is supposed to sine function and the demanded height is fixed. Same velocity makes same height regardless of diver's weight. So, the velocity of springboard when the feet of a diver are separated from the springboard is a main factor of the analysis. The result shows that there is no association between deformation and weight and also between velocity and weight. That is, the required force to reach a optimal height is fixed whatever the diver's weight is.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.50-57
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• 1997

A 600HP class high-speed gear driven 3-stage turbo-compressor (IGCC : Integrally Geared Centrifugal Compressor) driven by a 3600 rpm AC induction motor has been designed, of which low speed pinion runs at 35000 rpm and high speed pinion at 50000 rpm nominally. Due to its high speed operation, the system requires very reliable bearing selection and design as well as accurate rotordynamic analysis and prediction of its dynamic behavior to secure the operating reliability. Rotordaynamic analyses of the IGCC rotor-bearing system predicted that the low speed pinion rotor mounted on 5-pad tilting pad bearings has two critical speeds before its design speed and high speed pinion rotor only one critical speed, and estimated critical speeds of both pinion shafts are away from the continuous operating speed enough to satisfy the corresponding API requirement. The forced response analysis with API specified maximum allowable unbalances also showed that unbalance responses are small enough for smooth operation of the system.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1426-1434
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• 2008

This paper addresses the numerical study on the dynamics of the High-speed EMU to enhance the ride quality. The 17 and 34 degrees-of-freedom (DOF) dynamic models for a single railway vehicle are proposed, and its vibrational characteristics according to the nonuniform rail profile are analyzed via Matlab. The validity of the proposed 34-DOF model are verified by comparing its dynamic characteristics and those from ADAMS/Rail. In addition, the critical dynamic parameters are identified by the parametric analysis, and rough design variables to reduce the vibration level of the railway vehicle are proposed. Finally, the frequency analysis - FFT - are conducted to extract the resonant frequencies, which have a significant influence on the determination of the critical speed of the railway vehicle. It is demonstrated that the results from the Matlab-based numerical analysis of the 34-DOF dynamic model are similar to those from ADAMS/Rail.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.212-212
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• 2016

해수면 상승의 예측에 대한 근본적인 불확실성은 전 지구적 해수면 상승에 대한 가속도와 상대적으로 해수면에 영향을 미치는 지역적인 요소와 연관되어 있다. 최근, 기후 모형을 포함하는 다양한 모형의 결과와 빙하 관측자료, 그리고 이들의 해수면에 대한 기여도는 해수면 상승이 가속화될 것이라는 사실을 나타내지만, 아직 조수 관측과 위성 자료들은 이와 관련된 근거를 발견하지 못하고 있다. 본 논문에서는 연안도시 계획 설계자들이 이러한 해수면 상승의 불확실성을 고려할 수 있도록 미래 해수면 상승의 확률론적 산정을 제공하기 위해 최근 해수면 상승 가속과 그 상승률에 대해 선택된 분포와 관측 해수면 자료의 합성을 제시한다. 결과는 프로젝트 취약성을 평가하기 위한 위험도 기반 관리체계의 기준으로서 사용 될 수 있다. 또한, 기후 영향에 의한 해수면의 동역학적 지질물리학의 이해도를 증진시킴으로써, 분포의 선택과 정확성, 그리고 해수면 상승 예측이 개선될 것이라고 기대 된다. 본 연구에서 제시된 방법론은 사례연구로 부산에 적용되어 설명되어 진다.

• Journal of Ocean Engineering and Technology
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• v.28 no.5
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• pp.371-377
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• 2014

In this study, the hydrodynamic characteristics of various types of jack-up legs for a wind turbine installation vessel were analyzed. Using the modified Morison equation, the wave and current excitation forces on the jack-up legs were calculated. A modal analysis was performed to predict the dynamic responses for various types of jack-up legs. The Newmark-beta time integration scheme was used to solve the equation of motion in waves in the time domain. The maximum displacement and maximum bending stress were computed for four different types of legs, and their results were compared to select an optimum leg type. Finally, a six-leg jack-up rig with the selected optimal legs was modeled, and its natural period and hydrodynamic behaviors were evaluated.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.3
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• pp.27-36
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• 2000

A higher order panel method based on B-spline representation for both the geometry and the velocity potential is developed for the solution of the flow around two-dimensional lifting bodies. Unlike Lee/Kerwin, who placed multiple control points on each panel and solved the overdetermined system of equation by the least square approach, the present method places only as many number of control points as required by the unknowns of the problem. Especially, a null pressure jump Kutta condition at the trailing edge is found to be effective in stabilizing the solution process and in predicting the correct solution. The new approach, is validated to be accurate through comparison with the analytic solution for a 2-D airfoil and to be less time-consuming due to fewer number of panels required than that used in Lee/Kerwin.

• Journal of the Korean Society of Safety
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• v.22 no.5
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• pp.1-6
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• 2007

Vibro-impacts in manual transmissions result due to several nonlinearities such as multi-staged clutch characteristics and gear backlashes. For the sake of understanding the torsional system, one specific manual transmission with front engine and front wheel drive configuration is investigated with a linear model under the several assumptions substituting the nonlinear factors. First, this system is examined with the mathematical approaches by expressing the governing equations to find out the torsional motions. Second, this system is analyzed using the linear model in order to understand its modal and frequency response characteristics using eigensolution method and the FRF(Frequency Responses Function) analysis. Third, with the given results from the eigensolutions, several mode shapes are investigated related to the torsional motion characteristics. Fourth, the system characteristics with the FRFs are studied with the basic approach, with which the several key parameters will be suggested based upon the results in the further studies.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.4
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• pp.16-21
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• 2011

This paper described an analysis of dynamic mechanism for the industrial two-step folding automatic door using commercial software packages. Two modeling types of operating on the guide rail, the sliding one and the rolling, were adopted to investigate effects of impact force when the door ascends the guide rail. The magnitude of impact force was found very peaklike large over an initial duration of the door's moving up. The amount of damping coefficient for alleviating this shock was controlled to such a moderate degree that the operating conditions can be obtained for the purpose of design. Moreover the behavior of both dynamic stress and deformation were observed for acquirement of structural reliabilities of the combined guide rail and rolling mechanism. This research will be a very useful tool in the near future for the dynamic analysis of the multi-step folding automatic door.