• Journal of Korean Society for Atmospheric Environment
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• v.20 no.4
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• pp.523-537
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• 2004

In order to raise the accuracy of meteorological data, several numerical experiments about the usefulness of data assimilation to prediction of air pollution was carried out. Used data for data assimilation are surface meteorological components observed by Automatical Weather System with high spatial density. The usage of surface data assimilation gives changes of temperature and wind fields and the change caused by the influence of land-use on meterological simulation is more sensitive at night than noon. The data quality in assimilation it also one of the important factors to predict the meteorological field precisely and through the static IOA (Index of Agreement), simulated meteorological components with selected limited surface data assimilation are agree well with observations.

• Journal of Navigation and Port Research
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• v.30 no.4
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• pp.259-265
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• 2006

This paper presents an improved adaptive neural network autopilot based on our previous study for track-keeping control of ships. The proposed optimal neural network controller can automatically adapt its learning rate and number of iterations. Firstly, the track-keeping control system of ships is described For the track-keeping control task, a way-point based guidance system is applied To improve the track-keeping ability, the off-track distance caused by external disturbances is considered in learning process of neural network controller. The simulations of track-keeping performance are presented under the influence of sea current and wind as well as measurement noise. The toolbox for track-keeping simulation on Mercator chart is also introduced.

• Steel and Composite Structures
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• v.1 no.4
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• pp.377-392
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• 2001

The response of multi-story building structures to lateral loads, mainly due to earthquake and wind, is investigated for preliminary design purposes. Emphasis is placed on structural systems consisting of rigid and braced steel frames. An attempt to gain a qualitative understanding of the influence of bending and shear stiffness distribution on the deformations of such structures is made. This is achieved by modeling the structure with a stiffness equivalent Timoshenko beam. It is observed that the conventional stiffness distribution, dictated by strength constraints, may not be the best to satisfy deflection criteria. This is particularly the case for slender structural systems with prevailing bending deformations, such as flexible braced frames. This suggests that a new approach to the design of such frames may be appropriate when serviceability governs. A pertinent strategy for preliminary design purposes is proposed.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.265-268
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• 2006

Performed fatigue strength analysis for Hub to get the targeted service life of 20 years. ANSYS is used to analysis. The major structure of bearing which connect the hub and blades is modeled using the element of LINK10. To represent the stiffness of LINK10 element, initial strain and diameter of LINK10 element is applied. Prior to calculating the fatigue damages, the influence matrix is extracted from the unit loads. The target service life of 20 years is achieved from the Analysis results.

• Journal of Environmental Science International
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• v.11 no.7
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• pp.679-686
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• 2002

Turbulence greatly influence on atmospheric flow field. In the atmosphere, turbulence is represented as turbulent diffusion coefficients. To estimate turbulent diffusion coefficients in previous studies, it has been used constants or 2-level method which divides surface layer and Ekman layer. In this study, it was introduced Smagorinsky method which estimates turbulent diffusion coefficient not to divide the layer but to continue in vertical direction. We simulated 3-D flow model and TKE equation applied turbulent diffusion coefficients using two methods, respectively. Then we showed the values of TKE and the condition of each term to TKE. The results of Smagorinsky method were reasonable. But the results of 2-level method were not reasonable. Therefor, it had better use Smagorinsky method to estimate turbulent diffusion coefficients. We are expected that if it is developed better TKE equation and model with study of computational method in several turbulent diffusion coefficients for reasonably turbulent diffusion, we will able to predict precise wind field and movements of air pollutants.

• Journal of Navigation and Port Research
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• v.31 no.7
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• pp.563-568
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• 2007

In this paper, an adaptive neural network controller and its application to automatic berthing control of ship is presented. The neural network controller is trained online using adaptive interaction technique without any teaching data and off-line training phase. Firstly, the neural networks used to control rudder and propeller during automatic berthing process are presented. Secondly, computer simulations of automatic ship berthing are carried out in Pusan bay to verify the proposed controller under the influence of wind disturbance and measurement noise. The results of simulation show good performance of the developed berthing control system.

• 한국전산유체공학회:학술대회논문집
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• 2006.10a
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• pp.20-21
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• 2006

Three kinds of jet flows encountered in the practical airframe design phase are discussed in this paper. Firstly, the side jet effect on the cavity flow over the flat plate was investigated. Secondly, the aerodynamic modeling of side jet influence on body-tail configuration was presented. Computational study of the similarity parameters was done to minimize the wind tunnel test. Lastly, supersonic jet impingement on a flat plate surrounded by solid walls was simulated numerically for both axi-symmetric and three-dimensional calculations with moving body method.

• Journal of Ocean Engineering and Technology
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• v.37 no.5
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• pp.181-189
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• 2023

The fuel consumption of marine diesel engines holds paramount importance in contemporary maritime transportation and shapes energy efficiency strategies of ocean-going vessels. Nonetheless, a noticeable gap in knowledge prevails concerning the influence of ship hull conditions and propeller roughness on fuel consumption. This study bridges this gap by utilizing artificial intelligence techniques in Matlab, particularly convolutional neural networks (CNNs) to comprehensively investigate these factors. We propose a time-series prediction model that was built on numerical simulations and aimed at forecasting ship hull and propeller conditions. The model's accuracy was validated through a meticulous comparison of predictions with actual ship-hull and propeller conditions. Furthermore, we executed a comparative analysis juxtaposing predictive outcomes with navigational environmental factors encompassing wind speed, wave height, and ship loading conditions by the fuzzy clustering method. This research's significance lies in its pivotal role as a foundation for fostering a more intricate understanding of energy consumption within the realm of maritime transport.

• Wind and Structures
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• v.6 no.6
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• pp.419-436
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• 2003

Large-eddy simulations of the flow around a circular cylinder at a Reynolds number, based on cylinder diameter and free-stream velocity, $Re_D=2{\times}10^4$ are presented. Three different dynamic subgrid-scale models are used, viz. the dynamic eddy-viscosity model and two different mixed two-parameter models. The sensitivity to grid refinement in the spanwise and radial directions is systematically investigated. For the highest resolution considered, the effects of subgrid-scale modeling are also discussed in detail. In particular, it is shown that SGS modeling has a significant influence on the low-frequency modulations of the aerodynamics loads, which are related to significant changes in the near wake structure.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.52-56
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• 2011

Recently, KARI(Korea Aerospace Research Institute) has been developing a modern 11.5m diameter four bladed bearingless main rotor system, and this rotor system can be used for 7,000lb class helicopter. Flexbeam and torque tube can be considered as the key structural components, and large elastic twist of flexbeam induced by pitch control motion of torque tube can influence the nonlinear aeroelastic behavior. In this paper, the dynamic characteristic analysis results of bearingless rotor system were presented. In order to construct a input model and validate the analysis procedures, calculated results using the comprehensive helicopter analysis program CAMRAD II were compared with the measured natural frequencies and lag damping data from small-scale wind tunnel test. Next, the analysis model was extended to a full-scale model, and the dynamic analysis results were presented.