• Title/Summary/Keyword: Dynamic Grid

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Three-Dimensional Modeling and Simulation of a Phosphoric Acid Fuel Cell Stack (인산형 연료전지 스택에 대한 3차원 모델링 및 모사)

  • An Hyun-shik;Kim Hyo
    • Journal of the Korean Institute of Gas
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    • v.4 no.1 s.9
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    • pp.40-48
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    • 2000
  • A fuel cell is an electrochemical device continuously converting the chemical energy in a fuel and an oxidant to electrical energy by going through an essentially invariant electrode-electrolyte system. Phosphoric acid fuel cell employs concentrated phosphoric acid as an electrolyte. The cell stack in the fuel cell, which is the most important part of the fuel cell system, is made up of anode where oxidation of the fuel occurs cathode where reduction of the oxidant occurs; and electrolyte, to separate the anode and cathode and to conduct the ions between them. Fuel cell performance is associated with many parameters such as operating and design parameters associated with the system configuration. In order to understand the design concepts of the phosphoric fuel cell and predict it's performance, we have here introduced the simulation of the fuel-cell stack which is core component and modeled in a 3-dimensional grid space. The concentration of reactants and products, and the temperature distributions according to the flow rates of an oxidant are computed by the help of a computational fluid dynamic code, i.e., FLUENT.

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Transonic/Supersonic Nonlinear Aeroelastic Analysis of a Complete Aircraft Using High Speed Parallel Processing Technique (고속 병렬처리 기법을 이용한 전기체 항공기 형상의 천음속/초음속 비선형 공탄성 해석)

  • Kim, Dong-Hyun;Kwon, Hyuk-Jun;Lee, In;Kwon, Oh-Joon;Paek, Seung-Kil;Hyun, Yong-Hee
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.8
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    • pp.46-55
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    • 2002
  • A nonlinear aeroelastic analysis system in transonic and supersonic flows has been developed using high speed parallel processing technique on the network based PC-clustered machines. This paper includes the coupling of advanced numerical techniques such as computational structural dynamics (CSD), finite element method (FEM) and computational fluid dynamics (CFD). The unsteady Euler solver on dynamic unstructured meshes is employed and coupled with computational aeroelastic solvers. Thus it can give very accurate engineering data in the structural and aeroelastic design of flight vehicles. To show the great potential of useful application, transonic and supersonic flutter analyses have been conducted for a complete aircraft model under developing in Korea.

Soft-golfTM Shaft Kick Point and Stiffness due to the Difference in Performance Analysis (소프트 골프 샤프트의 킥 포인트와 강성의 차이에 따른 성능 분석)

  • Oh, H.Y.;Yu, M.;Kim, S.H.;Jang, J.H.;Kim, N.G.;Kim, D.W.
    • Journal of Biomedical Engineering Research
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    • v.31 no.3
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    • pp.227-233
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    • 2010
  • This study analyzed performance according to kick point and stiffness of Soft-golfTM shaft. This research team developed soft-golfTM as a new fusion sports with similar motions with golf and it can be learned safely for all age groups in 2002. The head of Soft-golfTM club is made of zinc alloy and has a mesh or a grid structure, and shaft uses carbon graphite to reduce the total weight of the club. To improve carry distance and to assure consistency of a ball during Soft-golfTM swing, this study manufactured shaft with various kick points (low, middle and high) and stiffness (stiff, regular, lady, morelady) and analyzed a swing motion with characteristics of each shaft presented in a dynamic condition such as a ball's speed, a head's torsion angle and a ball's deviation with ProAnalyst program through a high-speed camera taking pictures using a swing machine robot system(Robo-7). From all of the results, this study determined an appropriate shaft of Soft-golfTM.

Evaluation of wind loads and wind induced responses of a super-tall building by large eddy simulation

  • Lu, C.L.;Li, Q.S.;Huang, S.H.;Tuan, Alex Y.;Zhi, L.H.;Su, Sheng-chung
    • Wind and Structures
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    • v.23 no.4
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    • pp.313-350
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    • 2016
  • Taipei 101 Tower, which has 101 stories with height of 508 m, is located in Taipei where typhoons and earthquakes commonly occur. It is currently the second tallest building in the world. Therefore, the dynamic performance of the super-tall building under strong wind actions requires particular attentions. In this study, Large Eddy Simulation (LES) integrated with a new inflow turbulence generator and a new sub-grid scale (SGS) model was conducted to simulate the wind loads on the super-tall building. Three-dimensional finite element model of Taipei 101 Tower was established and used to evaluate the wind-induced responses of the high-rise structure based on the simulated wind forces. The numerical results were found to be consistent with those measured from a vibration monitoring system installed in the building. Furthermore, the equivalent static wind loads on the building, which were computed by the time-domain and frequency-domain analysis, respectively, were in satisfactory agreement with available wind tunnel testing results. It has been demonstrated through the validation studies that the numerical framework presented in this paper, including the recommended SGS model, the inflow turbulence generation technique and associated numerical treatments, is a useful tool for evaluation of the wind loads and wind-induced responses of tall buildings.

Dynamic Characteristics of Space Framed Structures by Using Nonlinear Transient Analysis (비선형 과도해석을 이용한 스페이스 프레임 구조물의 동적특성)

  • Son, Jin Hee;Kim, Joo-Woo
    • Journal of Korean Society of Steel Construction
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    • v.28 no.6
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    • pp.395-402
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    • 2016
  • Space frame structures considering the components such as forms, layers, grids, etc. are possible to form a large space without interior columns. Here, steels having the yield strengths of 210 MPa to 450 MPa are generally used. The high strength steel (i.e., yield strength of 690 MPa) having suitable weldability, aseismicity and economics have been recently developed. In this paper, the high strength steel is applied to the space frame structures in order to analytically find out their transient responses considering the material and geometric nonlinearities. For various circular dome types of space frame structures, the modal analysis and nonlinear transient analysis are carried out using nonlinear three dimensional finite element analysis.

Deep Neural Network Model For Short-term Electric Peak Load Forecasting (단기 전력 부하 첨두치 예측을 위한 심층 신경회로망 모델)

  • Hwang, Heesoo
    • Journal of the Korea Convergence Society
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    • v.9 no.5
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    • pp.1-6
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    • 2018
  • In smart grid an accurate load forecasting is crucial in planning resources, which aids in improving its operation efficiency and reducing the dynamic uncertainties of energy systems. Research in this area has included the use of shallow neural networks and other machine learning techniques to solve this problem. Recent researches in the field of computer vision and speech recognition, have shown great promise for Deep Neural Networks (DNN). To improve the performance of daily electric peak load forecasting the paper presents a new deep neural network model which has the architecture of two multi-layer neural networks being serially connected. The proposed network model is progressively pre-learned layer by layer ahead of learning the whole network. For both one day and two day ahead peak load forecasting the proposed models are trained and tested using four years of hourly load data obtained from the Korea Power Exchange (KPX).

Investigation of the observed solar coronal plasma in EUV and X-rays in non-equilibrium ionization state

  • Lee, Jin-Yi;Raymond, John C.;Reeves, Katharine K.;Shen, Chengcai;Moon, Yong-Jae
    • The Bulletin of The Korean Astronomical Society
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    • v.43 no.1
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    • pp.53.1-53.1
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    • 2018
  • During a major solar eruption, the erupting plasma is possibly out of the equilibrium ionization state because of its rapid heating or cooling. The non-equilibrium ionization process is important in a rapidly evolving system where the thermodynamical time scale is shorter than the ionization or recombination time scales. We investigate the effects of non-equilibrium ionization on EUV and X-ray observations by the Atmospheric Imaging Assembly (AIA) on board Solar Dynamic Observatory and X-ray Telescope (XRT) on board Hinode. For the investigation, first, we find the emissivities for all the lines of ions of elements using CHIANTI 8.07, and then we find the temperature responses multiplying the emissivities by the effective area for each AIA and XRT passband. Second, we obtain the ion fractions using a time-dependent ionization model (Shen et al. 2015), which uses an eigenvalue method, for all the lines of ion, as a function of temperature, and a characteristic time scale, net, where ne and t are density and time, respectively. Lastly, the ion fractions are multiplied to the temperature response for each passband, which results in a 2D grid for each combination of temperature and the characteristic time scale. This is the set of passband responses for plasma that is rapidly ionized in a current sheet or a shock. We investigate an observed event which has a relatively large uncertainty in an analysis using a differential emission measure method assuming equilibrium ionization state. We verify whether the observed coronal plasmas are in non-equilibrium or equilibrium ionization state using the passband responses.

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Typhoon Surge Simulation on the West Coast Incorporating Asymmetric Vortex and Wave Model on a Fine Finite Element Grid (상세유한요소격자에서 비대칭 경도풍과 파랑모형이 고려된 서해안의 태풍해일모의)

  • Suh, Seung-Won;Kim, Hyeon-Jeong
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.24 no.3
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    • pp.166-178
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    • 2012
  • In order to simulate storm surge for the west coast, complex physics of asymmetrical typhoon wind vortex, tide and wave are simultaneously incorporated on a fine finite element mesh extended to the North Western Pacific sea. Asymmetrical vortex based on maximum wind radii for each quadrant by JTWC's best tracks are input in pADCIRC and wave stress is accounted by dynamic coupling with unSWAN. Computations performed on parallel clusters. In hindcasting simulation of typhoon Kompasu(1007), model results of wave characteristic are very close with the observed data at Ieo island, and sea surface records at major tidal stations are reproduced with satisfaction when typhoon is approaching to the coast. It is obvious that increasing of local storm surges can be found by introducing asymmetrical vortex. Thus this approach can be satisfactorily applied in coastal hazard management against to storm surge inundation on low level area and major harbor facilities.

Nonlinear Simulation of Flutter Flight Test with the Forced Harmonic Motion of Control Surfaces (조종면 강제 조화운동을 고려한 비선형 플러터 비행시험 모사)

  • Yoo, Jae-Han;Kim, Dong-Hyun;Kwon, Hyuk-Jun;Lee, In;Kim, Young-Ik;Lee, Hee-Woo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.6
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    • pp.92-100
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    • 2002
  • In this study, transonic/supersonic nonlinear flutter analysis system of a complete aircraft including forced harmonic motion pf control surfaces has been effectively developed using the modified transonic small disturbance (TSD) equation. To consider the nonlinear effects, the coupled time marching method (CTM) combining computational structural dynamics (CFD) has been directly applied for aeroelastic computations. The grid system for a complex full aircraft configuration is effectively generated by the developed inhouse code. Intransonic and supersonic flight regimes, the characteristics of static and dynamic aeroelastic effect has been investigated for a complete aircraft model. Also, nonlinear flutter flight simulations for the forced harmonic motion of control surfaces are practically presented in detail.

A Numerical Simulation of Blizzard Caused by Polar Low at King Sejong Station, Antarctica (극 저기압(Polar Low) 통과에 의해 발생한 남극 세종기지 강풍 사례 모의 연구)

  • Kwon, Hataek;Park, Sang-Jong;Lee, Solji;Kim, Seong-Joong;Kim, Baek-Min
    • Atmosphere
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    • v.26 no.2
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    • pp.277-288
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    • 2016
  • Polar lows are intense mesoscale cyclones that mainly occur over the sea in polar regions. Owing to their small spatial scale of a diameter less than 1000 km, simulating polar lows is a challenging task. At King Sejong station in West Antartica, polar lows are often observed. Despite the recent significant climatic changes observed over West Antarctica, adequate validation of regional simulations of extreme weather events such as polar lows are rare for this region. To address this gap, simulation results from a recent version of the Polar Weather Research and Forecasting model (Polar WRF) covering Antartic Peninsula at a high horizontal resolution of 3 km are validated against near-surface meteorological observations. We selected a case of high wind speed event on 7 January 2013 recorded at Automatic Meteorological Observation Station (AMOS) in King Sejong station, Antarctica. It is revealed by in situ observations, numerical weather prediction, and reanalysis fields that the synoptic and mesoscale environment of the strong wind event was due to the passage of a strong mesoscale polar low of center pressure 950 hPa. Verifying model results from 3 km grid resolution simulation against AMOS observation showed that high skill in simulating wind speed and surface pressure with a bias of 1.1ms1 and -1.2 hPa, respectively. Our evaluation suggests that the Polar WRF can be used as a useful dynamic downscaling tool for the simulation of Antartic weather systems and the near-surface meteorological instruments installed in King Sejong station can provide invaluable data for polar low studies over West Antartica.