• Journal of the Korean earth science society
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• v.39 no.4
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• pp.317-326
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• 2018

Effect of the nonuniform grid on the two-dimensional transport equation was investigated in terms of theoretical analysis and finite difference method (FDM). The nonuniform grid having a typical structure of the numerical weather forecast model was incorporated in the vertical direction, while the uniform grid was used in the zonal direction. The staggered and non-staggered grid were placed in the vertical and zonal direction, respectively. Time stepping was performed with the third-order Runge Kutta scheme. An error analysis of the spatial discretization on the nonuniform grid was carried out, which indicated that the combined effect of the nonuniform grid and advection velocity produced either numerical diffusion or numerical adverse-diffusion. An analytic function is used for the quantitative evaluation of the errors associated with the discretized transport equation. Numerical experiments with the non-uniformity of vertical grid were found to support the analysis.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.51-55
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• 2004

A composite Iso-grid panel is manufactured and tested by compressive load. Vertical stringers and side stringers are joined with skin by secondary bonding using a liquid type adhesive. Bonding fixtures were developed to attach the stringers to skin. A-scan was done for inspection of secondary bonding region. The out of displacement field is visualized by shadow moire system. The strain and vertical displacement are measured by strain gages and L VDT (Linear Variable Differential Transformer). A local buckling is occurred at all grid sections. After that, the final failure is occurred. The strain of side stringer is much less than that of vertical stringer and skin. Due to the side stringer, the local buckling is delayed. Therefore the ratio of the first buckling to failure load is greater than that of vertical stringer stiffened panel.

• Journal of the Korean earth science society
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• v.40 no.4
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• pp.382-391
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• 2019

The impact of vertical grid-nesting on the tropical cyclone intensity and track forecast was investigated using the Weather Research and Forecast (WRF) version 3.8 and the initialization method of the Structure Adjustable Balanced Bogus Vortex (SABV). For a better resolution in the central part of the numerical domain, where the tropical cyclone of interest is located, a horizontal and vertical nesting technique was employed. Simulations of the tropical cyclone Sanba (16th in 2012) indicated that the vertical nesting had a weak impact on the cyclone intensity and little impact on the track forecast. Further experiments revealed that the performance of forecast was quite sensitive to the horizontal resolution, which is in agreement with previous studies. The improvement is due to the fact that horizontal resolution can improve forecasts not only on the tropical cyclone-scale but also for large-scale disturbances.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.1
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• pp.151-159
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• 2020

This study aimed to investigate the performance characteristics of vertical axis turbine of tidal energy convertor. Three-dimensional Reynolds-averaged Navier-Stokes equation with shear stress transport turbulence model has been solved to analyze the fluid flow of the vertical axis turbine. The hexahedral grids have been used to construct the computational domain and the grid dependency test has been performed to find the optimum grid system. Four steps have been carried out to design the vertical axis turbine of the 100 kW class tidal energy convertor.

• 한국전산유체공학회:학술대회논문집
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• 2002.10a
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• pp.150-155
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• 2002

A commercial CFD code is applied to analyze the 3-D viscous flow field within vertical multi-stage centrifugal pump including impeller with 6 blades and guide vane with 11 blades and is performed by changing flow rate from 10 to $26m^3/h$ at the constant 3500rpm. The purpose of this 3-D numerical simulation is not only to confirm how much the effect of three kinds of blade inlet breadth (11mm, 11.5mm, 12mm) of impeller has influence on the performance of vertical multi-stage pump but also to make clear the cause about performance difference at the exit side of impeller and guide vane. The vertical multi-stage pump consisit of the impeller, guide, vane and cylinder. The grid of numerical analysis used to the vertical multi-stage pump is 18,000, 45,000, and 100000 cells in case of the impeller, guide vane, cylinder and total grid is 730,000 cells. The characteristics such as total pressure coefficient, total head, shaft horse power, power efficiency at the exit side of impeller and guide vane, discharge coefficient are represented according to flow rage changing.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2007.04a
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• pp.179-182
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• 2007

In this study, we proposed a way to detect trees using virtual grid and to discriminate vertical wall points from building tops based on effective segmentation of LIDAR point cloud utilizing scan line characteristics. Trees were detected by their surface roughness value calculated based on virtual grid and vertical building wall points were discriminated from building tops with one dimensional filtering of scan line during segmenting point cloud. In results, we could distinguish trees from buildings and bind virtical wall points to prevent them from faltly acting on point segmentation process.

• Journal of Environmental Impact Assessment
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• v.20 no.4
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• pp.575-583
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• 2011

In this study, the plausible grid size was estimated to increase for efficiency of reservoir management using 3 dimensional water quality model. To validate utilization of a real time water quality management tool, ELCOM-CAEDYM model was applied to Soyang reservoir in korea. 100m grid size can represent the real topography and take out exact analysis results. $400{\times}400m$ grid can be easily used to analysis because of data capacity. Consequently, the grid size of 200m or 300m was recommended to establish 3D model considering the required simulation time and the irrelevance between horizontal grid size and vertical distribution for temperature and turbidity analysis.

• Atmosphere
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• v.25 no.3
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• pp.529-541
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• 2015

Korea Institute of Atmospheric Prediction System (KIAPS) has been developing a global numerial prediction model and data assimilation system. We has implemented LETKF (Local Ensemble Transform Kalman Filter, Hunt et al., 2007) data assimilation system to NCAR CAM-SE (National Center for Atmospheric Research Community Atmosphere Model with Spectral Element dynamical core, Dennis et al., 2012) that has cubed-sphere grid, known as the same grid system of KIAPS Integrated Model (KIM) now developing. In this study, we have assimilated Global Positioning System Radio Occultation (GPS-RO) bending angle measurements in addition to conventional data within ensemble-based data assimilation system. Before assimilating bending angle data, we performed a vertical unit conversion. The information of vertical localization for GPS-RO data is given by the unit of meter, but the vertical localization method in the LETKF system is based on pressure unit. Therefore, with a clever conversion of the vertical information, we have conducted experiments to search for the best vertical localization scale on GPS-RO data under the Observing System Simulation Experiments (OSSEs). As a result, we found the optimal setting of vertical localization for the GPS-RO bending angle data assimilation. We plan to apply the selected localization strategy to the LETKF system implemented to KIM which is expected to give better analysis of GPS-RO data assimilation due to much higher model top.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.12
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• pp.65-72
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• 2018

The purpose of this study is to predict vertical illuminance accurately at the design stage of a building without the help of simulation tools. Comparing two well-known vertical illuminance prediction algorithms with measured values, it is verified that the Igawa model is more consistent with the measured values than the Perez model. Using the DIVA program, we simulated the vertical illuminance at 30-degree intervals from south to north, compared with the vertical illuminance calculated with the Igawa model. The result of calculation values were verified from 120 degrees east to 120 degrees west. The vertical illuminance values with each of three shade devices were calculated using the Igawa model, and compared with the vertical illuminance simulated by DIVA program. As a result, all the errors when installing horizontal / vertical / grid shade divices were included in the error standard specified by ASHRAE.

• Journal of KIISE
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• v.43 no.9
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• pp.1026-1033
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• 2016

Path-finding on a grid map is a problem generally addressed in the fields of robotics, intelligent agents, and computer games. As technology advances, virtual game worlds tend to be represented more accurately and more realistically, resulting in an excessive increase in the number of grid tiles and in path-search time. In this study, we propose a path-finding algorithm that allows a prompt response to real-time queries by constructing a reduced state space and by precomputing all possible paths in an offline preprocessing stage. In the preprocessing stage, we vertically decompose free space on the grid map, construct a connectivity graph where nodes are the decomposed regions, and store paths between all pairs of nodes in matrix form. In the real-time query stage, we first find the nodes containing the query points and then retrieve the corresponding stored path. The proposed method is simulated for a set of maps that has been used as a benchmark for grid-based path finding. The simulation results show that the state space and the search time decrease significantly.