• Title/Summary/Keyword: Dynamic Grid

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The assessment of the relative contribution of the shape of instantaneous unit hydrograph with heterogeneity of drainage path (배수경로 이질성에 의한 순간단위도 형상의 상대적 기여도 평가)

  • Choi, Yong-Joon;Kim, Joo-Cheol;Kim, Jae-Han
    • Journal of Korea Water Resources Association
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    • v.42 no.11
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    • pp.897-909
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    • 2009
  • The relative contribution of between hillslope-flow and stream-flow by heterogeneity of drainage path are quantitatively assessed in the present study with GIUH model based on grid of GIS. Application watersheds are selected Pyeongchang, Bocheong and Wi river basin of IHP in Korea. The mean and variance of hillslope and stream length are estimated and analyzed in each watershed. And coupling with observation storm events, estimate hillslope and stream characteristic velocity which dynamic parameters of GIUH model. The mean and variance of distribution of travel time (i.e. IUH) calculate using estimated pass lengths and characteristic velocities. And the relative contributions are assessed by heterogeneity of drainage path. As a result, the effect of the variance that determine shape of IUH dominate with hillslope's effect in the small watershed area (within 500 km2). Thus, GIUH in the small watershed area must consider hillslope-flow.

Generating high resolution of daily mean temperature using statistical models (통계적모형을 통한 고해상도 일별 평균기온 산정)

  • Yoon, Sanghoo
    • Journal of the Korean Data and Information Science Society
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    • v.27 no.5
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    • pp.1215-1224
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    • 2016
  • Climate information of the high resolution grid units is an important factor to explain the phenomenon in a variety of research field. Statistical linear interpolation models are computationally inexpensive and applicable to any climate data compared to the dynamic simulation method at regional scales. In this paper, we considered four different linear-based statistical interpolation models: general linear model, generalized additive model, spatial linear regression model, and Bayesian spatial linear regression model. The climate variable of interest was the daily mean temperature, where the spatial variability was explained using geographic terrain information: latitude, longitude, elevation. The data were collected by weather stations in January from 2003 and 2012. In the sense of RMSE and correlation coefficient, Bayesian spatial linear regression model showed better performance in reflecting the spatial pattern compared to the other models.

Dynamic Analysis of AP1000 Shield Building Considering Fluid and Structure Interaction Effects

  • Xu, Qiang;Chen, Jianyun;Zhang, Chaobi;Li, Jing;Zhao, Chunfeng
    • Nuclear Engineering and Technology
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    • v.48 no.1
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    • pp.246-258
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    • 2016
  • The shield building of AP1000 was designed to protect the steel containment vessel of the nuclear reactor. Therefore, the safety and integrity must be ensured during the plant life in any conditions such as an earthquake. The aim of this paper is to study the effect of water in the water tank on the response of the AP1000 shield building when subjected to three-dimensional seismic ground acceleration. The smoothed particle hydrodynamics method (SPH) and finite element method (FEM) coupling method is used to numerically simulate the fluid and structure interaction (FSI) between water in the water tank and the AP1000 shield building. Then the grid convergence of FEM and SPH for the AP1000 shield building is analyzed. Next the modal analysis of the AP1000 shield building with various water levels (WLs) in the water tank is taken. Meanwhile, the pressure due to sloshing and oscillation of the water in the gravity drain water tank is studied. The influences of the height of water in the water tank on the time history of acceleration of the AP1000 shield building are discussed, as well as the distributions of amplification, acceleration, displacement, and stresses of the AP1000 shield building. Research on the relationship between the WLs in the water tank and the response spectrums of the structure are also taken. The results show that the high WL in the water tank can limit the vibration of the AP1000 shield building and can more efficiently dissipate the kinetic energy of the AP1000 shield building by fluid-structure interaction.

Reynolds and froude number effect on the flow past an interface-piercing circular cylinder

  • Koo, Bonguk;Yang, Jianming;Yeon, Seong Mo;Stern, Frederick
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.6 no.3
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    • pp.529-561
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    • 2014
  • The two-phase turbulent flow past an interface-piercing circular cylinder is studied using a high-fidelity orthogonal curvilinear grid solver with a Lagrangian dynamic subgrid-scale model for large-eddy simulation and a coupled level set and volume of fluid method for air-water interface tracking. The simulations cover the sub-critical and critical and post critical regimes of the Reynolds and sub and super-critical Froude numbers in order to investigate the effect of both dimensionless parameters on the flow. Significant changes in flow features near the air-water interface were observed as the Reynolds number was increased from the sub-critical to the critical regime. The interface makes the separation point near the interface much delayed for all Reynolds numbers. The separation region at intermediate depths is remarkably reduced for the critical Reynolds number regime. The deep flow resembles the single-phase turbulent flow past a circular cylinder, but includes the effect of the free-surface and the limited span length for sub-critical Reynolds numbers. At different Froude numbers, the air-water interface exhibits significantly changed structures, including breaking bow waves with splashes and bubbles at high Froude numbers. Instantaneous and mean flow features such as interface structures, vortex shedding, Reynolds stresses, and vorticity transport are also analyzed. The results are compared with reference experimental data available in the literature. The deep flow is also compared with the single-phase turbulent flow past a circular cylinder in the similar ranges of Reynolds numbers. Discussion is provided concerning the limitations of the current simulations and available experimental data along with future research.

Study on Leading-phase Operation Capability of a 770 MW Jumbo Hydro-generator based on Stability Analysis and End-Region Heat Analysis

  • Fan, Zhen-nan;Zhou, Zhi-ting;Li, Jian-fu;Wen, Kun;Wang, Jun;Sun, Zhang;Wang, Tao;Yao, Bing
    • Journal of Electrical Engineering and Technology
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    • v.13 no.3
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    • pp.1317-1325
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    • 2018
  • A generator-grid coupling calculation model is established to study the leading-phase operational capability of a 770 MW jumbo hydro-generator in a Chinese ultra-mega hydropower station. The static and dynamic stability of the generator are analyzed and calculated to obtain stability limits under leading-phase operating conditions. Three-dimensional (3D) time-varying nonlinear moving electromagnetic and temperature field models of the generator end-region are also established and used to determine the magnetic field, loss, and temperature of the end-region under the leading-phase operating condition. The simulation results agree with data measured from the actual 770 MW hydro-generator. This paper provides reliable reference data for the leading-phase operation of a jumbo hydro-generator, which will help to improve in the design and manufacture of future hydro-generators.

Study on the Propagation Speed of the wide-area power system frequency for the application of FNET (광역 전력계통 주파수 감시망 적용을 위한 광역계통주파수의 전파속도에 관한 연구)

  • Kook, Kyung-Soo;Rho, Dae-Seok
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.10 no.8
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    • pp.1824-1831
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    • 2009
  • This paper analyzes the propagation speed of the wide-area power system frequency. When a generator supplying the electric power to the grid is accidently tripped due to a disturbance on the systems, power system frequency suddenly drops during the transient period and this propagates from the location of the tripped generator to the other part of the systems like a wave. Since the propagation speed of the power system frequency depends on the own characteristics of power systems, its understanding from the perspective of the wide-area can help us in understanding power systems more correctly. In addition, the propagation speed of the power system frequency is used as a key parameter in the application study of IT based on the internet-based GPS synchronized frequency monitoring network (FENT) which has been recently implemented and operated in U.S. power systems. This paper simulates the generation trip on various locations in U.S. power systems deploying its latest dynamic model and calculates the propagation speed of the power system frequency for the application of FNET.

Big Data Processing and Performance Improvement for Ship Trajectory using MapReduce Technique

  • Kim, Kwang-Il;Kim, Joo-Sung
    • Journal of the Korea Society of Computer and Information
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    • v.24 no.10
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    • pp.65-70
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    • 2019
  • In recently, ship trajectory data consisting of ship position, speed, course, and so on can be obtained from the Automatic Identification System device with which all ships should be equipped. These data are gathered more than 2GB every day at a crowed sea port and used for analysis of ship traffic statistic and patterns. In this study, we propose a method to process ship trajectory data efficiently with distributed computing resources using MapReduce algorithm. In data preprocessing phase, ship dynamic and static data are integrated into target dataset and filtered out ship trajectory that is not of interest. In mapping phase, we convert ship's position to Geohash code, and assign Geohash and ship MMSI to key and value. In reducing phase, key-value pairs are sorted according to the same key value and counted the ship traffic number in a grid cell. To evaluate the proposed method, we implemented it and compared it with IALA waterway risk assessment program(IWRAP) in their performance. The data processing performance improve 1 to 4 times that of the existing ship trajectory analysis program.

A Study on the Web Application for Sailing Ship Location Information interface based by RIA (RIA기반의 선박항해정보를 위한 웹 애플리케이션 구축 "평택항 원양어선 항해정보현황 사례를 중심으로")

  • Jung, Hoe-Jun;Park, Dea-Woo;Han, Kyung-Don
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2009.10a
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    • pp.613-616
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    • 2009
  • Information present condition is using situation board by manual processing that is consisted of ship arrangement plan and letterpress and magnet etc. in Pyeongtaekhang's deep-sea fishing vessel company. Study that mark open sea far from land ship information of underway 37 ships that is accepted in every time in internet web application environment that is based on Ubiquitous Network in PC that is linked to internet. 3 through practical use of RIA of Flash technology base compose Digital Dash-Board in width grid structure only and do ship sailing addition that is operating in 6 oceans and latitude, hardness indication as well as various informations to do visual display do. Emphasized in dynamic Web Application construction because can heighten the convenience to operator and user, and take advantage of real time data.

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Effect of Heat Transfer and Phase Change of Coolant on the Performance of Mixed-gas Ejection System (냉각제의 분사조건 및 상변화가 혼합가스 사출시스템의 성능에 미치는 영향)

  • Kim, Hyun Muk;Kim, Jeong Soo
    • Journal of the Korean Society of Propulsion Engineers
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    • v.22 no.6
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    • pp.84-93
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    • 2018
  • Three-dimensional (3D) numerical simulations have been carried out to study how coolant injection conditions influence the cooling efficiency and projectile ejection performance in a mixture-gas ejection system (or gas-steam launch system). The 3D single-phase computational model was verified using a 1D model constructed with reference to the previous research and then a two-phase flow computation simulating coolant injection on to hot gas was performed using a DPM (Discrete Phase Model). As a result of varying the coolant flow rate and number of injection holes, cooling efficiency was improved when the number of injection holes were increased. In addition, the change of the coalescence frequency and spatial distribution of coolant droplets caused by the injection condition variation resulted in a change of the droplet diameter, affecting the evaporation rate of coolant. The evaporation was found to be a critical factor in the design optimization of the ejection system by suppressing the pressure drop while the temperature decreases inside the breech.

Prediction of Resistance and Planing Attitude for Prismatic Planing Hull using OpenFOAM (OpenFOAM을 이용한 주형체 활주선의 저항 및 항주자세 추정)

  • Shi, XiangYu;Zhang, Yang;Yum, Deuk-joon
    • Journal of Ocean Engineering and Technology
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    • v.33 no.4
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    • pp.313-321
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    • 2019
  • The prediction of the hydrodynamic performance of a planing hull vessel is an important and challenging topic for computational fluid dynamic (CFD) applications to naval hydrodynamics. In this paper, the resistance and planing attitude analysis for a Fridsma hull, which is a prismatic planing hull, in still water are numerically studied using OpenFOAM. OpenFOAM is an open source code package based on C++ libraries and the finite volume method (FVM) for the discretization of the RANS equation. The volume of fluid method (VOF) is used to capture the water-air interface and the SST κω model is used for the turbulence simulation. The overset mesh method is used to capture the large motion of the hull at higher speeds. Before the extensive analysis, uncertainty analyses using various time steps and grid sizes were performed for one ship speed case of Fn = 1.19. The results of the present study are compared with those of a model test, other CFD research, and Savitsky's empirical formula. The results of the present study, following the trend of other CFD results, slightly over predict the resistance and under predict the sinkage and, more significantly, the trim.