• Title/Summary/Keyword: the numerical analysis

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A Study on Numerical Analysis Using the Two Phase Flow in Alkaline Water Electrolysis Stacks (알카리 수전해 스택에서 수소기포의 2상유동 수치해석에 관한 연구)

  • HAN, JINMOK;BAE, YOOGEUN;SEO, YOUNGJIN;KIM, SEWOONG;JUNG, YOUNGGUAN
    • Transactions of the Korean hydrogen and new energy society
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    • v.29 no.2
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    • pp.155-162
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    • 2018
  • In this paper, the reliability of the numerical analysis using the two phase flow on the behavior of the hydrogen bubbles in the alkali electrolysis stacks was investigated by comparing the results obtained from numerical analysis and flow visualization experiments. As the results, through comparison with results gotten to visualization experiments, it is possible to approximate analysis for the flow of hydrogen bubbles in the stacks by numerical analysis using the two-phase flow. Also, the flow of hydrogen bubbles around the electrodes could be similarly analyzed by numerical analysis using the two-phase flow.

In-Plane Buckling of Prime and Quadratic Parabolic Arches with Fixed Ends (양단고정 Prime과 Quadratic 포물선 아치의 면내좌굴에 관한 연구)

  • 이병구;김종만
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.29 no.3
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    • pp.153-162
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    • 1987
  • A numerical procedure for the analysis of slender arch buckling problems for uniform dead weight is presented in this paper. Such loading changes in the arch profile. The problem is nonlinear. The numerical procedure is limited to an inextensible analysis and to elastic behavior. Based upon a numerical integration technique developed by Newmark for straight beams, a large deflection bending analysis is combined with small deflection buckling routines to formulate the numerical procedure. The numerical procedure is composed of a combination of the numerical integration and successive approximations procedure. The results obtained in this study are as follows : 1.The critical loads obtained in this study coincide with the results by Austin so that the algorithm developed in this study is verified. 2.The numerical results are converged with good precision when the half arch is divided into 10 segments in both Prime and Quadratic section. 3.The critical loads are decreased as the ratios of rise versus span are increased. 4.The critical loads are increased as the moments of inertia at the ends are increased. 5.The critical loads of Prime section are larger than that of Quadratic section under the same profile conditions.

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A GUIDE FOR NUMERICAL WIND TUNNEL ANALYSIS IN ORDER TO PREDICT WIND LOAD ON A BUILDING (건축물의 풍하중을 예측하기 위한 수치풍동기법)

  • Lee, Mung-Sung;Lee, June-Hee;Hur, Nahm-Keon;Choi, Chang-Koon
    • 한국전산유체공학회:학술대회논문집
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    • 2010.05a
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    • pp.5-9
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    • 2010
  • A numerical wind tunnel simulation is performed in order to predict wind loads acting on a building. The aim of the present study is to suggest a guideline for the numerical wind tunnel analysis, which could provide more detail wind load distributions compared to the wind code and expensive wind tunnel experiments. To validate the present numerical simulation, wind-induced loads on a 6 m cube model is predicted. Atmospheric boundary layer is used as a inlet boundary condition. Various effect of numerical methods are investigated such as size of computational domain, grid density, turbulence model and discretization scheme. The appropriate procedure for the numerical wind tunnel analysis is suggested through the present study.

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On the Numerical Stability of Dynamic Reliability Analysis Method (동적 신뢰성 해석 기법의 수치 안정성에 관하여)

  • Lee, Do-Geun;Ok, Seung-Yong
    • Journal of the Korean Society of Safety
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    • v.35 no.3
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    • pp.49-57
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    • 2020
  • In comparison with the existing static reliability analysis methods, the dynamic reliability analysis(DyRA) method is more suitable for estimating the failure probability of a structure subjected to earthquake excitations because it can take into account the frequency characteristics and damping capacity of the structure. However, the DyRA is known to have an issue of numerical stability due to the uncertainty in random sampling of the earthquake excitations. In order to solve this numerical stability issue in the DyRA approach, this study proposed two earthquake-scale factors. The first factor is defined as the ratio of the first earthquake excitation over the maximum value of the remaining excitations, and the second factor is defined as the condition number of the matrix consisting of the earthquake excitations. Then, we have performed parametric studies of two factors on numerical stability of the DyRA method. In illustrative example, it was clearly confirmed that the two factors can be used to verify the numerical stability of the proposed DyRA method. However, there exists a difference between the two factors. The first factor showed some overlapping region between the stable results and the unstable results so that it requires some additional reliability analysis to guarantee the stability of the DyRA method. On the contrary, the second factor clearly distinguished the stable and unstable results of the DyRA method without any overlapping region. Therefore, the second factor can be said to be better than the first factor as the criterion to determine whether or not the proposed DyRA method guarantees its numerical stability. In addition, the accuracy of the numerical analysis results of the proposed DyRA has been verified in comparison with those of the existing first-order reliability method(FORM), Monte Carlo simulation(MCS) method and subset simulation method(SSM). The comparative results confirmed that the proposed DyRA method can provide accurate and reliable estimation of the structural failure probability while maintaining the superior numerical efficiency over the existing methods.

Composite Discharge Capacity Analysis of Vertical Drain Installed in Ground (연직배수재가 타설된 지반의 복합통수능 해석)

  • Kim, Chang-Young;Kwak, No-Kyung;Lee, Song
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.10a
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    • pp.1167-1174
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    • 2008
  • Vertical drain method, which is one of the soft ground improvement methods, shorten s drain path to accelerate consolidation process and is applied in many sites. At a recent, composite discharge capacity experiment that analyze discharge amount by consolidation behavior with overburden pressure of soft ground in laboratory, simulates similarly with actuality. Geotechnical engineering problems such a s soft ground improvement are solved by numerical analysis by development of computer and numerical analysis techniques. Numerical analysis does that result is contrary by user's inexperience for choice of constitution model and application of analysis method. Therefore, this thesis experiments on composite discharge capacity test and study discharge capacity of drain and consolidation behavior of soft ground installed prefabricated vertical drain boards. Also, This thesis studied reasonable input parameters and constitution model by compare results of composite discharge capacity test and numerical analysis using PLAXIS that is 2D finial element numerical analysis program.

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Analytic and Numerical Study for air Bubble Defect of UV-NIL Process (UV-NIL 공정의 기포 결함에 대한 해석적 및 수치적 연구)

  • Seok, Jeong-Min;Kim, Nam-Woong
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.21 no.3
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    • pp.473-478
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    • 2012
  • In this paper, the air bubble formation mechanism in the rectangular and triangular line-and-space pattern during dispensing UV Nanoimprint Lithography (UV-NIL) at an atmospheric condition is studied. To investigate the air bubble formation, an analytic model based on geometric approach and a numerical model based on CFD(computational fluid dynamics) were used in the analysis. It was found in the numerical analysis that every time the flow front passed through a corner of the pattern, it proceeded with a newly formed shape, occurring due to interface reconfiguration, since the flow fronts were formed such that they minimized the surface energy. Moreover, the conditions for the air bubble formation were investigated by applying the analytic analysis based on geometric approach and the numerical analysis. Good overall agreement was found between the analytic and numerical analysis.

A study on the cracking of tunnel lining by measurement and numerical analysis (계측 및 수치해석을 통한 터널 라이닝의 균열 원인 연구)

  • Hwang, Hak;Jung, Hun-Chul;Kim, Yu-Seok
    • Proceedings of the Korean Geotechical Society Conference
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    • 2001.03a
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    • pp.33-40
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    • 2001
  • In this research, the cracking of tunnel concrete lining was investigated and analyzed through long-term measurement and nonlinear numerical analysis. For one year after the casting of lining, the stresses and strains were measured by the sensors installed in hard rock tunnel lining. The measurements showed that only small stresses which were less than cracking stress occurred in every survey sections regardless of sensor directions. It could be induced that the external load applied to the lining was small or ignorable. Also, it was carried out short-term numerical analysis based on such site condition as ambient temperature, the- degree of overbreak and mold staying period. Long-term numerical analysis based on creep & shrinkage and nonlinear cracking was carried out. The output showed that construction condition and ambient environments could make the lining concrete crack without external loads. The cracks formed in this process does not indicate the structural instability of the tunnel.

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2-D Consolidation Numerical Analysis of Multi_Layered Soils (다층 지반의 2차원 압밀 수치해석)

  • 김팔규;류권일;남상규;이재식
    • Proceedings of the Korean Geotechical Society Conference
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    • 2000.03b
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    • pp.467-474
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    • 2000
  • The application of Terzaghi's theory of consolidation for analysing the settlement of multi-layered soils is not strictly valid because the theory involves an assumption that the soil is homogeneous. The settlement of stratified soils with confined aquifer can be analysed using numerical techniques whereby the governing differential equation is replaced by 2-dimensional finite difference approximations. The problems of discontinuous layer interface are very important in the algorithm and programming for the analysis of multi-layered consolidation using a numerical analysis, finite difference method(F.D.M.). Better results can be obtained by the process for discontinuous layer interface, since it can help consolidation analysis to model the actual ground The purpose of this paper provides an efficient computer algorithm based on numerical analysis using finite difference method(F.D.M) which account for multi-layered soils with confined aquifer to determine the degree of consolidation and excess pore pressures relative to time and positions more realistically.

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Evaluation of Internal Settlement of Rockfill Dam under Construction (석괴댐의 축조 중 내부 침하 거동 평가)

  • Seo, Min-Woo;Kim, Yong-Seong
    • Journal of The Korean Society of Agricultural Engineers
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    • v.52 no.4
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    • pp.45-52
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    • 2010
  • The purposes of this research are to analyze the internal settlement behavior of Concrete Faced Rockfill Dam (CFRD) typed 'D dam' and to evaluate the stability of the 'D dam' during dam construction using internal settlement measurements and results of numerical analysis. The field measurements were obtained during dam construction period. The numerical analysis was also carried out for the same construction period. The numerical analysis focused mainly on prediction of stress and displacement behavior of 'D dam' during dam construction stage using input parameters obtained from laboratory tests, i.e. large triaxial tests. The behavior of 'D dam' was evaluated to be stable from comparing the results of field measurements and numerical analysis. A simple empirical equation is also presented to predict final settlement at the completion of dam construction, using settlement measurement monitored during dam embankment.

Effect of element size in hybrid stress analysis around a hole in loaded orthotropic composites (직교이방성 재료의 구멍주위에 관한 하이브리드 응력해석시 요소크기의 효과)

  • Baek, Tae-Hyun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.10
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    • pp.1702-1711
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    • 1997
  • A numerical study for the number of terms of a power series stress function and the effect of hybrid element size on stress analysis around a hole in loaded orthotropic composites is presented. The hybrid method coupling experimental and/or theoretical inputs and complex variable formulations involving conformal mappings and analytical continuity is used to calculate tangential stress on the boundary of the hole in uniaxially loaded, finite width glass epoxy tensile plate. The tests are done by rarying the number of terms, element size and nodal locations on the external boundary of the hybrid region. The numerical results indicate that the hybrid method is accurate and powerful in both experimental and numerical stress analysis.