• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 창립기념 춘계학술대회 논문집
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• pp.494-501
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• 1998

This Paper describes the evaluation methods and criteria used to verify running Performance of railway vehicle, and shows results of vehicle dynamics simulation and running performance tests for New Mugunghwa Coaches that were designed and manufactured by DHI in 1997. Through running performance test of New Mugunghwa Coaches, Vibration, Ride Comfort were measured on the condition of service operation. As a results, each simulation and test results meet the criteria proposed by Korean National Railroad(KNR) and Korea Railroad Research Institute(KRRI).

• 한국철도학회논문집
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• 제9권6호
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• pp.792-797
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• 2006

In general, the Maglev vehicle is ran over the elevated guideway consisted of steel or concrete structure. Since the running behaviour of the vehicle is affected by the flexibility of the guideway, the consideration of the flexibility of guideway is needed for evaluation of dynamics of both the vehicle and guideway. A new technique based on flexible multibody dynamics is proposed to model the Maglev vehicle, levitation controller, and guideway into a coupled model. To verify the technique, an urban Maglev vehicle is analyzed using the technique and discussions are carried out.

• 한국정밀공학회지
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• 제28권5호
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• pp.543-550
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• 2011

The development of railway vehicles such as new mechanism of railway vehicle or design parameters of suspension have been used the application of scaled roller rig to the study of railway vehicle dynamics. In this paper, the critical speed was compared between full scale and 1:5 scale of numerical model. And to verify the simulation results, the critical speed was confirmed using the 1:5 scaled roller rig. According to the results, we expect that the developed roller rig will be used in the study for the dynamic characteristics of railway vehicle.

• Wind and Structures
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• 제20권2호
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• pp.143-168
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• 2015

A numerical model for analyzing air-train-track interaction is proposed to investigate the dynamic behavior of a high-speed train running on a track in crosswinds. The model is composed of a train-track interaction model and a train-air interaction model. The train-track interaction model is built on the basis of the vehicle-track coupled dynamics theory. The train-air interaction model is developed based on the train aerodynamics, in which the Arbitrary Lagrangian-Eulerian (ALE) method is employed to deal with the dynamic boundary between the train and the air. Based on the air-train-track model, characteristics of flow structure around a high-speed train are described and the dynamic behavior of the high-speed train running on track in crosswinds is investigated. Results show that the dynamic indices of the head car are larger than those of other cars in crosswinds. From the viewpoint of dynamic safety evaluation, the running safety of the train in crosswinds is basically controlled by the head car. Compared with the generally used assessment indices of running safety such as the derailment coefficient and the wheel-load reduction ratio, the overturning coefficient will overestimate the running safety of a train on a track under crosswind condition. It is suggested to use the wheel-load reduction ratio and the lateral wheel-rail force as the dominant safety assessment indices when high-speed trains run in crosswinds.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.1782-1793
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• 2008

Republic of korea has begun operating high speed train service according as KTX service operation starts in 2004. Also, EMU whose maximum speed is over 150 kph will be starting to service with electrification and improvement of existing railroad. Moreover, metropolitan electric railways have begun an express service to increase scheduled speed. Therefore, running resistance of rolling stock becomes more important factor effects on the performance. Running resistance of rolling stock is the factor which is necessary for the performance or operation plan of rolling stock, and it's related to rolling friction, slip friction, drag force, gradient, acceleration, curvature, tunnel condition and so on. It is possible to be calculated by CFD (Computational Fluid Dynamics). However it is predicted by experimental equation from running resistance test because of the complex calculation and manifold variables. In this paper, studies about running resistance of rolling stock is introduced, and each term of experimental equation is studied through theoretical approximation. Also, running resistance of rolling stock is estimated by the result of running resistance test, and effects being related to friction, drag force, gradient is examined.

• 대한조선학회논문집
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• 제59권3호
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• pp.173-182
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• 2022

The present study suggests a procedure of establishing a ship dynamics modeling by regression of free-running model test results. The hydrodynamic force and moment of the whole model ship is derived from the low-pass filtered acceleration in the turning circle and zigzag maneuver tests. Force and moment of the propeller and rudder are separated from that of the whole ship to acquire the hull force and moment terms, based on the principles of the component model. The low-pass filter frequency is verified in prior to dynamics modeling, to find the threshold frequency of 2.5 Hz. The dynamics modeling of the hull is compared with the component modeling by captive model tests. Because of strong correlation between sway velocity, yaw angular velocity, and heel angle, each maneuvering coefficient is not able to be validated, but the whole modeling shows good agreement with the captive model tests.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2006년도 추계학술대회 특별세미나 특별세션
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• pp.229-238
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• 2006

In general, the Maglev vehicle is run over an elevated guideway consisting of steel or concrete structure. Since the running behavior of the vehicle is affected by the flexibility of the guideway, the consideration of the flexibility of guideway is needed for evaluating the dynamics of both the vehicle and guideway. A new method based on flexible multibody dynamics is proposed to model the Maglew vehicle. This method combines the levitation controller, vehicle, and guideway into a coupled model To verify the method, an urban transit is analyzed using the method and discussions are carried out.

• 한국운동역학회지
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• 제19권4호
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• pp.663-669
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• 2009

본 연구의 목적은 런닝 턴 동작시 많은 정확한 턴을 위한 방법으로 발의 움직임을 역학적으로 분석하기 위함이다. 런닝 턴 동작에 대한 많은 역학적인 요인들 중 정확한 턴을 위해서는 감속이 발생되고 이런 감속은 진행하고자 하는 방향으로 턴을 할 수 있게 해준다. 턴이 시작되는 시점인 발의 회전각과 이로 발생되는 몸통의 각을 3차원 영상분석과 지면반력 분석을 하였다. 따라서, 여러 매개변수들 중 수직축(z축)에서 발의 총 회전각($\theta_f$)/몸통 총 회전각($\theta_d$)= 발의 효과($\varepsilon$)로 단순화 시켜 간단한 방정식을 만들어서 설명했으며, 자료 산출을 위해 평균 속력 4.5m/s에서 진행 방향 $0^{\circ}$, $30^{\circ}$, $60^{\circ}$ 턴에 대한 분석을 통해 턴의 각이 커지면 커질수록 입각기 시간, 발 변위, 좌 우힘이 증가했음을 알 수 있었다.

• 대한조선학회논문집
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• 제56권1호
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• pp.23-33
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• 2019

Unmanned Surface Vehicle (USV) is being developed to do maritime survey and maritime surveillance at Korea Research Institute of Ships & Ocean engineering (KRISO). The goal is that USV should be operated at the maximum speed of 45 knots and it should be operated at sea state 4. Therefore the planing hull of USV should be excellent in resistance performance and manoeuvring performance. It is needed to check its performance using Experimental Fluid Dynamics (EFD), Computational Fluid Dynamics (CFD) or analytic method before designing the hull. In this study, resistance performance was analyzed by EFD and CFD. EFD with heave and pitch was performed at high speed towing system in Seoul National University. CFD was performed using SNUFOAM based on openFOAM with dynamic mesh to calculate running attitudes. The results of CFD were compared with EFD results. The results of CFD were resistance, running attitudes and wave height. The flow distribution and pressure distribution were also analyzed. The results of numerical resistance was under estimated than EFD. Even though the results of CFD have a slight limitation, it can be successfully used to estimate the resistance performance of planing hull. In addition it can be used as a supplement for EFD results.

• Wind and Structures
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• 제20권2호
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• pp.169-189
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• 2015

To investigate the effects of "sudden change" of wind fluctuations on vehicle running performance, which is caused by the artificial discrete simulation of wind field, a three-dimensional vehicle model is set up with multi-body dynamics theory and the vehicle dynamic responses in crosswind conditions are obtained in time domain. Based on Hilbert Huang Transform, the effects of simulation separations on time-frequency characteristics of wind field are discussed. In addition, the probability density distribution of "sudden change" of wind fluctuations is displayed, addressing the effects of simulation separation, mean wind speed and vehicle speed on the "sudden change" of wind fluctuations. The "sudden change" of vehicle dynamic responses, which is due to the discontinuity of wind fluctuations on moving vehicle, is also analyzed. With Principal Component Analysis, the comprehensive evaluation of vehicle running performance in crosswind conditions at different simulation separations of wind field is investigated. The results demonstrate that the artificial discrete simulation of wind field often causes "sudden change" in the wind fluctuations and the corresponding vehicle dynamic responses are noticeably affected. It provides a theoretical foundation for the choice of a suitable simulation separation of wind field in engineering application.