• Title/Summary/Keyword: 3-D numerical analysis

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NUMERICAL SIMULATION OF THE FLOW CHARACTERISTICS INSIDE A U-TYPE TUBE (U-자형 곡관내의 유동특성에 대한 수치해석적 연구)

  • Koh, D.H.;Kang, D.J.;Song, D.J.
    • Journal of computational fluids engineering
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    • v.14 no.3
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    • pp.105-114
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    • 2009
  • A numerical study of the flow characteristics inside a U-type circular tube is carried out in this paper. The numerical simulations carried out by using a Navier-Stokes code which is commercially available. Before detailed numerical simulations, validation of present numerical approach is made by comparing numerical solutions with experimental data. Numerical simulations are performed to study the effect of curvature on the flow characteristics inside a U-type tube. Numerical solutions show that a significant effect on the secondary flow structure in the cross section of the tube, especially in the curved section is shown when the curvature ratio, ratio of curvature to tube diameter, is smaller than about 3.5. As the curvature ratio decreases below 3.5, a counter rotating vortex is found below the primary vortex in the cross section of the tube. Another dramatic change of the flow structure is the formation of streamwise separation zone when the curvature ratio is decreased below 1.25.

Estimation of Total Displacements by RMR Grades using 3-Dimensional Numerical Analysis (3D 수치해석을 이용한 퇴적암 터널의 암반 등급별 전변위 산정)

  • Yim, Sung-Bin;Yun, Hyun-Seok;Seo, Yong-Seok;Park, Si-Hyun
    • The Journal of Engineering Geology
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    • v.17 no.2 s.52
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    • pp.217-224
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    • 2007
  • Tunnel displacement happens during the process of stress redistribution by tunnelling. Tunnel displacement can be divided into 3 types such as displacements occurring before excavation, non-measured displacements after excavation and measured displacements after excavation. Because measurements of displacements occurring before excavation and non-measured displacement after excavation are difficult and time-consuming in the field, many researchers have studied on total displacement and its characteristics with excavation using numerical analysis. In this study, we used a 3-D back analysis to estimate total displacement by rock mass grades in tunnel constructed in sedimentary rock. We reduced error between measured displacements and calculated displacements from a 3-D numerical analysis, and then estimated suitable rock mass properties by RMR classes. Ultimately, Logistic nonlinear regressions of total displacement with tunnelling were estimated by least square estimation.

NUMERICAL ANALYSIS OF FLOW CHARACTERISTIC WITH DIFFERENT CORNER RADIUS OF SQUARE CYLINDER

  • Gao, Zhefeng;Sohn, Chang-Hyun
    • 한국전산유체공학회:학술대회논문집
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    • 2010.05a
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    • pp.315-319
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    • 2010
  • The near wake of square section cylinders with different corner radii is studied by numerical method to investigate the influence of corner radius. Eight models, R/D=0, 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5 (R is the corner radius and D is the characteristic dimension of the body) at Re=500 were studied. The numerical results of St, CD and CL at R/D=0 and R/D=0.5 were compared with experiments to prove the feasibility and also investigate the trend of flow phenomena by the various radius corners. Results indicate that, as R/D ratio is increased, the Strouha lnumber is increased, the minimum pressure point on the cylinder surface moved own stream. The calculated results shows that between R/D=0.15 to R/D=0.3 have CD and CL.

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Study on 3D Numerical Analysis of Stack Effect Reduction in Stairwell of Building (건축물 계단에서의 연돌효과 저감방안에 대한 3차원 수치해석 연구)

  • Kim, Jung-Yup;Kim, Ji-Seok
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.27 no.3
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    • pp.152-157
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    • 2015
  • Stack effect on high-rise building have negative effect on living environment, energy and life-safety aspect. Thus, it's necessary to find the measure to reduce the stack effect. As a result of field test on a 31-story building, a circulating type stack effect reduction technology was developed, which supplies air in the low stairs and discharges air in the high stairs. To evaluate the performance of this circulating type stack effect reduction technology on building stairs, a 3D numerical analysis was carried out by using Momentum Loss Model for analyzing leakage flow between compartments in a building. Consequently, numerical analysis proved that the stack effect on building stairs was reduced by a circulating type stack effect reduction technology.

Evaluation of Dynamic Behavior for Pile-Supported Slab Track System by 3D Numerical Analysis (3차원 수치해석을 통한 궤도지지말뚝의 동적거동 평가)

  • Yoo, Mintaek;Back, Mincheol;Lee, Ilhwa;Lee, Jinsun
    • Journal of the Earthquake Engineering Society of Korea
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    • v.21 no.5
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    • pp.255-264
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    • 2017
  • Dynamic numerical simulation of pile-supported slab track system embedded in a soft soil and embankment was performed. 3D model was formulated in a time domain to consider the non-linearity of soil by utilizing FLAC 3D, which is a finite difference method program. Soil non-linearity was simulated by adopting the hysteric damping model and liner elements, which could consider soil-pile interface. The long period seismic loads, Hachinohe type strong motions, were applied for estimating seismic respose of the system, Parametric study was carried out by changing subsoil layer profile, embankment height and seismic loading conditions. The most of horizontal permanent displacement was initiated by slope failure. Increase of the embedded height and thickness of the soft soil layer leads increase of member forces of PHC piles; bending moment, and axial force. Finally, basic guidelines for designing pile-supported slab track system under seismic loading are recommended based on the analysis results.

NUMERICAL ANALYSIS OF THREE DIMENSIONAL SUPERSONIC CAVITY FLOW FOR THE VARIATION OF CAVITY SPANWISE RATIO (3차원 공동의 폭변화에 따른 초음속 유동에 대한 수치분석연구)

  • Woo, C.H.;Kim, J.S.;Choi, H.I.
    • 한국전산유체공학회:학술대회논문집
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    • 2006.10a
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    • pp.181-184
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    • 2006
  • High-speed flight vehicle have various cavities. The supersonic cavity flow is complicated due to vortices, flow separation and reattachment, shock and expansion waves. The general cavity flow phenomena include the formation and dissipation of vortices, which induce oscillation and noise. The oscillation and noise greatly affect flow control, chemical reaction, and heat transfer processes. The supersonic cavity' flow with high Reynolds number is characterized by the pressure oscillation due to turbulent shear layer, cavity geometry, and resonance phenomenon based on external flow conditions, The resonance phenomena can damage the structures around the cavity and negatively affect aerodynamic performance and stability. In the present study, we performed numerical analysis of cavities by applying the unsteady, compressible three dimensional Reynolds-Averaged Navier-Stokes(RANS) equations with the ${\kappa}-{\omega}$ turbulence model. The cavity model used for numerical calculation had a depth(D) of 15mm cavity aspect ratio(L/D) of 3, width to spanwise ratio(W/D) of 1.0 to 5.0. Based on the PSD(Power Spectral Density) and CSD(Cross Spectral Density) analysis of the pressure variation, the dominant frequency was analyized and compared with the results of Rossiter's Eq.

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NUMERICAL ANALYSIS OF THREE DIMENSIONAL SUPERSONIC CAVITY FLOW FOR THE VARIATION OF CAVITY SPANWISE RATIO (공동의 폭 변화에 따른 3차원 초음속 공동 유동연구)

  • Woo, C.H.;Kim, J.S.
    • Journal of computational fluids engineering
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    • v.11 no.4 s.35
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    • pp.62-66
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    • 2006
  • High-speed flight vehicle have various cavities. The supersonic cavity flow is complicated due to vortices, flow separation, reattachment, shock waves and expansion waves. The general cavity flow phenomena includes the formation and dissipation of vortices, which induce oscillation and noise. The oscillation and noise greatly affect flow control, chemical reaction, and heat transfer processes. The supersonic cavity flow with high Reynolds number is characterized by the pressure oscillation due to turbulent shear layer, cavity geometry, and resonance phenomenon based on external flow conditions. The resonance phenomena can damage the structures around the cavity and negatively affect aerodynamic performance and stability. In the present study, we performed numerical analysis of cavities by applying the unsteady, compressible three dimensional Reynolds-Averaged Navier-Stokes(RANS) equations with the ${\kappa}-{\omega}$ turbulence model. The cavity model used for numerical calculation had a depth(D) of 15mm cavity aspect ratio (L/D) of 3, width to spanwise ratio(W/D) of 1.0 to 5.0. Based on the PSD(Power Spectral Density) and CSD(Cross Spectral Density) analysis of the pressure variation, the dominant frequency was analyzed and compared with the results of Rossiter's Eq.

A Study on the Application of GIS for Analysis of Subsidence Hazard (지반침하 피해도 분석을 위한 GIS 활용에 관한 연구)

  • 권광수;유명환;박형동
    • Economic and Environmental Geology
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    • v.33 no.6
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    • pp.557-563
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    • 2000
  • Subsidence hazard has never been considered seriously until recent yews in Korea, although its socioeconomic impact on Korea becomes more and more enormous. There have been a few studies for the application of GIS analysis technique to the prediction of subsidence hazard. For GIS analysis, several factors, which are represented by coverage, are considered and selected for building a GIS model. Numerical method was used to quantify the importance of each factor in GIS model and the result from numerical modeling using FLAC was compared with that from previous research based on empirical methods. Analysis in 3-D needs more computer resources (i.e. memory). Therefore that in 2.5-D was considered to overcome the problem. Not only maximum vertical subsidence but also maximum horizontal strain and maximum slope have been considered for the assessment of subsidence hazard. The model can be easily modified for the purpose of applications in any subsidence area, especially cavern or abandoned mines under thick soil layer.

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Application of 3-D Numerical Wave Tank for Dynamic Analysis of Nonlinear Interaction between Tsunami and Vegetation (쓰나미-식생 비선형 상호작용의 동적해석을 위한 3차원 수치파동수조의 적용)

  • Lee, Woo-Dong;Hur, Dong-Soo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.36 no.5
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    • pp.831-838
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    • 2016
  • The disaster preventing system using vegetation has been growing in the field of coastal engineering in recent years. To analyze wave and flow fields under nonlinear interactions between tsunami and vegetation, the purpose of this study is to evaluate newly-developed 3-D numerical wave tank including energy dissipation by tsunami-vegetation interaction based on existing N-S solver with porous body model. Comparing numerical results using mean drag coefficient and dynamic drag coefficient due to Reynolds number to existing experimental results it is revealed that computed results considering the dynamic drag coefficient are in good agreement with the laboratory test results for time-domain waveform. In addition, the calculated transmission coefficients of solitary waves in various vegetation densities and incident wave heights are also in good agreement with the experimental values. This confirms the validity and effectiveness of the developed 3-D numerical wave tank with the fluid resistance by vegetation.

A Dual-Scale Analysis of Macroscopic Resin Flow in Vacuum Assisted Resin Transfer Molding Process (VARTM공정에서의 거시적 수지 유동의 Dual-Scale 분석)

  • 박윤희;강문구;이우일
    • Composites Research
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    • v.15 no.6
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    • pp.1-7
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    • 2002
  • In VARTM process where a sacrificial medium is used to facilitate the resin flow, the velocity of resin varies drastically between the sacrificial medium and the fiber preform. Although the thickness-to-length ratio of a VARTM product is usually small, a 3-D analysis is prerequisite to analyze the lead-lag flow in the two different media. The problem associated with the full 3-D analysis is the CPU time. A full 3-D numerical mesh comprising large number of nodes requires an impractical CPU time on average computer platforms. In this study, a dual-scale analysis technique was developed. The flow analysis for the entire calculation domain was conducted in 2.5-D, and the 3-D analysis was performed for a small area of special concern. In some numerical examples, the local 3-D analysis could discover an eccentric flow pattern as well as the lead-lag flow that will inevitably be neglected in 2.5-D simulations. The global-local analysis technique practiced in this study can be used to analyze the intricate flow of resin through non-uniform media in affordable CPU times.