• Title, Summary, Keyword: numerical analysis

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Analysis of Hydraulic Characteristics in the Middle Reaches of Nak-Dong River using 2-Dimensional Numerical Analyis Model (2차원 수치해석모형을 이용한 낙동강 중류구간의 하천흐름 해석)

  • Han, Sung-Dea;Choi, Hyun;Ahn, Chang-Hwan;Lee, Je-Yun
    • Proceedings of the Korea Water Resources Association Conference
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    • pp.1732-1736
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    • 2008
  • The characteristics of a river flow analysis are significant for river maintenance plan. At the present time, HEC-RAS, 1-Dimensional Numerical Analysis Model, is mainly applied to analyze the character of a river flow. The shape of a river is somewhat in longitudinal linear form. It was suspected that the usage of 1-dimensional numerical analysis model is more economical. Development of numerical analysis models and computers are possible to calculate large volume. Hence, it is possible to adapt the analysis of the key stations by 2-dimensional numerical analysis model. The limitation of 1-Dimensional Numerical Analysis Model is that it is hard to evaluate structure affection of numerical simulation by energy loss coefficient at river structure analyzing. When adaptation of the 2-dimensional numerical analysis model in river structure ensues, it takes more objective analyzing than 1-dimensional numerical analysis model for flow affection by river structure. 2-dimensional numerical analysis model consults with the different structure position of hydraulic characteristics and different water depth of shape and scope in vertical flow. 1-dimensional numerical analysis model is possible to simulate with only energy loss coefficient for sudden river section changing, sudden waterway changing by curved. 2-dimensional numerical analysis model use original geographical features. So the model removes technical subjectivity of faulty judgment. It is an objective analysis.

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A Comparative Study on Hydraulic Characteristics of Curved Channel by Hydraulic Model Experiments and Numerical Analysis (수리모형과 수치해석을 통한 만곡부 하천의 수리학적 특성 비교 고찰)

  • Seo, Dong-Il;Choi, Han-Kuy
    • Journal of Industrial Technology
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    • v.27 no.A
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    • pp.85-94
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    • 2007
  • This study, regarding curved channel, was performed to compare and analyze hydraulic characteristics and the speed of water and water level for left bank and right bank through hydraulic model experiments and numerical analysis. Real channels that had characteristics of curved channel were selected as objectives. In order to easily operate one and two dimensional numerical analysis and comparison for total 2.4Km model channel, measuring point was set up as 200m. HEC-RAS model was applied as one dimensional numerical analysis program and SMS model was used as two dimensional numerical analysis program. In respect of speed of water, the average speed of water for right bank recorded 8.33m/s in a model experiment and 3.08m/s, 8.57m/s were average speed of water for right bank in one dimensional and two dimensional numerical analysis. The average speed of water of two dimensional numerical analysis was quite similar to that of model experiments. Also, as for water level, maximum observational errors between one and two dimensional numerical analysis for right and left bank of model experiments were 0.66m, 0.84m and 0.28m, 0.48m for each. It was found that two dimensional numerical analysis had a similar result to hydraulic model experiments. Accordingly, from the result of this study, two dimensional numerical analysis should be used rather than one dimensional numerical analysis, when numerical analysis for curved channel is conducted.

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The study on the possibility of performance analysis for the compressive member using the numerical method (수치해석법을 활용한 압축부재 성능 해석의 가능성에 대한 연구)

  • Kim, Gwang-Chul
    • Journal of the Korea Furniture Society
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    • v.21 no.1
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    • pp.26-39
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    • 2010
  • This is a leading study to replace the structural analysis methodology on the specific traditional joint by a numerical analysis. Tests were carried out to test the compressive methodologies with the numerical results. The Japanese larch was used as a sample. The Orthotropic property of wood was specifically considered for the finite element numerical analysis. Linear numerical analysis and non-linear numerical analysis for the BEAM element and the two SOLID elements of ANSYS were used to analyze the compressive performance. In addition, more finely divided elements were used to raise the accuracy of the numerical result. Finally, the statistically significant differences were tested between that of the analytical and numerical results. It could be concluded that the SOLID 64 element shows the most optimum result when the non-linear analysis with the more finely divided element was used. However, finely dividing of the element is a considerable time consuming process, and it is quite difficult to raise the accuracy of the non-linear numerical analysis. Therefore, if considering the vertical displacement to be of the only interest, the BEAM element is more efficient than the SOLID element because the BEAM element is reflected as a simple line, which is less time consuming and difficult in dividing the elements. But, the BEAM element cannot accurately model the knot as a strength defect factor which is an important property in the orthotropic property of wood. Therefore, the SOLID element should be used to model the strength defect factor, knot, as it can be efficiently applied on the structural size flexure member which could be more strongly effected by the knot. In addition, it is useful at times when the failure types of members are to be more closely investigated, as the SOLID element is able to examine the local stress distribution of the member. The conclusion drawn by this study is of the good concordance between analytical results and numerical results of compressive wood members, but how orthotropic properties should only be considered. The numerical analysis on the specific Korean traditional joints will be based on the current study results.

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A Study on the Application of Load Distribution Factor through the Three-Dimensional Numerical Analysis in Tunnel (터널의 3차원 수치해석에서 하중분배율 적용에 관한 연구)

  • Yoon, Won-Sub;Cho, Chul-Hyun;Park, Sang-Jun;Kim, Jong-Kook;Chae, Young-Su
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.784-791
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    • 2008
  • In this study, we recognized about application of the load distribution factor for design of tunnel in 3D numerical analysis. Generally, load distribution factor of tunnel is applied to describe 3D arching effect that can not describe when 2D numerical analysis. Through result of 3D numerical analysis, we used to apply in numerical analysis for the load distribution factor that ratio of finally displacement to displacement of construction step. But 3D numerical analysis need to apply to load distribution factor for convenience of numerical analysis. Therefore, we proposed load distribution factor that reduce time and coast. It corrected variable of advanced length in load distribution factor of 3D numerical analysis.

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A Study of the Stream Specific by River Width's Downsizing & Extension (하천폭의 국부적 축소 및 확대에 따른 수리특성 연구)

  • Choi, Han-Kuy;Kim, Ju-Suk;Baek, Hyo-Sun
    • Journal of Industrial Technology
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    • v.27 no.B
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    • pp.229-233
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    • 2007
  • This research investigated the way of generating the flowing of water in case of artificial fluctuation of river width by the unidimensional numerical analysis in order to reconstruct vertical and expanse features of flowing, and the problem of existing numerical analysis in accordance with local enlargement and reduction of river through hydraulic model experiments with results of numerical analysis. The result revealed that when the local section change in the same river is exist, it showed 0.93m in the case of no change of local section in the hydraulic model experiments and numerical analysis, however, it presented 1.645m on the occasion of local section changes in the hydraulic model experiments and numerical analysis. In other words, there was a significant difference in the existing numerical analysis, when there was a local section change. As a result of the experimental section for the enlargement and reduction of local river width, due to the sensitive change for fluctuation of flood discharge, there was a significant difference between numerical analysis and hydraulic model experiments. In addition, the result of comparison between the enlargement and reduction of local river width confirmed that the result of numerical analysis with hydraulic model experiments showed larger generation of deviation in case of enlargement of section than in case of reduction of section.

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Applying the Polder Levee of the Stream Specific by Using Hydordynamic Model (수치해석을 이용한 윤중제 흐름특성해석 적용성)

  • Choi, Han-Kuy;Kim, Jang-Uk;Baek, Hyo-Sun
    • Journal of Industrial Technology
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    • v.28 no.B
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    • pp.193-198
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    • 2008
  • When the existing polder levee was constructed, the river's numerical analysis decided the bank raise by applying the planned flood stage or by using the result from the sectional 1st dimensional numerical analysis. But, it was presented that there is a limitation in the 1st dimensional value analysis when the structure like the polder levee obstructs the special shaped running water flow. Therefore, in order to verify the numerical value applicability when the polder levee is constructed, this report compared each other through the 1st and 2nd dimensional numerical analysis and the mathematical principle model laboratory. In case of the polder levee construction through the numerical analysis and the mathematical principle model laboratory, it was decided that there was no big problem in the 1st dimensional numerical analysis applied design, considering the uncertainty of mathematical principle analysis though the first dimensional numerical analysis was calculated a little bigger than the second. But, after construction, it was found that the water level deviation of the 1st, 2nd occurred biggest at the place where the flow was divided into two. Also, as a result of comparing the 1st, 2nd dimensional numerical analysis with the mathematical principle model laboratory, it was confirmed that the 1st numerical analysis applied design decreased the modal safety largely, as the left side water level was calculated smaller more than 0.5m in case of the 1st dimensional numerical analysis.

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Application of Numerical Differentiations in Free Vibration Analysis (자유진동 해석에서 수치미분의 응용)

  • 이병구;안대순;강희종;김권식
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.814-818
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    • 2003
  • This paper deals with the application of numerical differentiation in free vibration analysis. In the free vibration analysis, the derivative values of the given function are certainly used in calculation of structural parameters. For deriving the derivative values, both the time and labor are needed when the structures consist of non-linear geometries such as arches or curved beams. From this viewpoint, the numerical differentiation scheme is applied into the free vibration analysis. The numerical results obtained from the numerical differentiations are agreed very well with those obtained from the exact derivatives by analytical method. It is expected that the numerical differentiations can be utilized practically in the free vibration analysis.

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Computations of Numerical Deviations of Equations for Souring Depth Comparing with 1-D and 2-D Numerical Model (1, 2차원 수치해석에 따른 기존 세굴심 산정식 편차 산정)

  • Choi, Han-Kuy;Park, Tae-Hyun;Lee, Yeong-Seop
    • Journal of Industrial Technology
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    • v.28 no.B
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    • pp.185-191
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    • 2008
  • This study tried the 1st, 2nd dimensional numerical analysis according to the pier's shape, size and installing method in order to compare the depth of scour calculation method using the variables calculated by using the 2nd dimensional numerical analysis with the calculated depth of scour value by using the calculated variables by using the 1st dimensional numerical analysis. And then verified the problems occurring when the depth of scour is calculated by using the calculated values by using the 1st dimensional numerical analysis, as calculating the deviation depending on it.

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Augmented Displacement Load Method for Nonlinear Semi-analytical Design Sensitivity Analysis (준해석적 비선형 설계민감도를 위한 개선된 변위하중법)

  • Lee, Min-Uk;Yoo, Jung-Hun;Lee, Tae-Hee
    • Proceedings of the KSME Conference
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    • pp.492-497
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    • 2004
  • Three methods for design sensitivity such as numerical differentiation, analytical method and semi-analytical method have been developed for the last three decades. Although analytical design sensitivity analysis is exact, it is hard to implement for practical design problems. Therefore, numerical method such as finite difference method is widely used to simply obtain the design sensitivity in most cases. The numerical differentiation is sufficiently accurate and reliable for most linear problems. However, it turns out that the numerical differentiation is inefficient and inaccurate because its computational cost depends on the number of design variables and large numerical errors can be included especially in nonlinear design sensitivity analysis. Thus semi-analytical method is more suitable for complicated design problems. Moreover semi-analytical method is easy to be performed in design procedure, which can be coupled with an analysis solver such as commercial finite element package. In this paper, implementation procedure for the semi-analytical design sensitivity analysis outside of the commercial finite element package is studied and computational technique is proposed, which evaluates the pseudo-load for design sensitivity analysis easily by using the design variation of corresponding internal nodal forces. Errors in semi-analytical design sensitivity analysis are examined and numerical examples are illustrated to confirm the reduction of numerical error considerably.

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