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

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Study on Numerical Model of Leakage Flow at Gap between Compartments in a Building (건축물 구획실간 틈새에서의 누설유동에 대한 수치모델 연구)

  • Kim, Jung-Yup;Kim, Ji-Seok
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.25 no.10
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    • pp.562-567
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    • 2013
  • 1D-numerical analysis of the network algorithm with the orifice equation for the relationship between pressure difference and flowrate has been mostly used to analyse leakage flow at the gap. In this study, a 3D-numerical method applying momentum loss model to the gap region in the computational domain is represented to reflect effectively the effect of leakage flow by determining the proportion of pressure difference to air passage velocity. While the 3D-numerical method is verified through the computation of the two compartments model, the numerical analysis of the stack effect in a building stairway is performed. As the temperature of air outside drops, the pressure in the upper stairway and leakage flowrate through the gap in the door rise. The change of gap area does not have an effect on pressure in the stairway for the analysis conditions.

Seismic Analyses of Soil Pressure against Embedded Mat Foundation and Pile Displacements for a Building in Moderate Seismic Area (중진지역 건축물의 묻힌온통기초에 작용하는 토압과 말 뚝변위에 대한 지진해석)

  • Kim, Yong-Seok
    • Journal of the Earthquake Engineering Society of Korea
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    • v.21 no.1
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    • pp.69-76
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    • 2017
  • Seismic analyses of a pile under a large rigid basement foundation embedded in the homogeneous soil layer were performed practically by a response displacement method assuming a sinusoidal wave form. However, it is hard to take into account the characteristics of a large mat foundation and a heterogeneous soil layer with the response displacement method. The response displacement method is relevant to the 2D problems for longitudinal structures such as tunnel, underground cave structure, etc., but might not be relevant with isolated foundations for building structures. In this study, seismic pile analysis by a pseudo 3D finite element method was carried out to compare numerical results with results of the response displacement method considering 3D characteristics of a foundation-soil system which is important for the building foundation analyses. Study results show that seismic analyses results of a response displacement method are similar to those of a pseudo 3D numerical method for stiff and dense soil layers, but they are too conservative for a soft soil layer inducing large soil pressures on the foundation wall and large pile displacements due to ignored foundation rigidity and resistance.

Application of 3-D Numerical Method (LES-WASS-3D) to Estimation of Nearshore Current at Songdo Beach with Submerged Breakwaters (잠제가 설치 된 부산 송도해수욕장의 해빈류 예측에 관한 3차원 수치해석기법(LES-WASS-3D)의 적용)

  • Hur, Dong-Soo;Lee, Woo-Dong;Kim, Myoung-Kyu;Yoon, Jong-Sung
    • Journal of Ocean Engineering and Technology
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    • v.27 no.4
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    • pp.14-21
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    • 2013
  • This study examined the field application of a 3-D numerical model (LES-WASS-3D) to the estimation of the nearshore current at Songdo beach, Busan. The wave and tide conditions observed at Songdo beach during Typhoon Ewiniar (July 10, 2006) were used in a numerical simulation. The numerical wave heights were in good agreement with the field data. The spatial distributions of the wave heights, mean water levels, and mean flows obtained from the numerical simulation are discussed in relation to the bottom topographical change near Songdo beach before and after Typhoon Ewiniar. The results revealed that LES-WASS-3D is a powerful tool for estimating the nearshore current in the field.

A Numerical and Experimental Study on Dynamics of A Towed Low-Tension Cable

  • Jung, D.H.;Park, H.I.;Koterayama, W.
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • pp.191-196
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    • 2002
  • The paper presents a numerical and experimental investigation on dynamic behaviors of a towed low tension cable. In the numerical study, an implicit finite difference algorithm is employed for three-dimensional cable equations. Fluid and geometric non-linearity and bending stiffness are considered and solved by Newton-Raphson iteration. Block tri-diagonal matrix method is applied for the fast calculation of the huge size of matrices. In order to verify the numerical results and to see real physical phenomena, an experiment is carried out for a 6m cable in a deep and long towing tank. The cable is towed in two different ways; one is towed at a constant speed and the other is towed at a constant speed with top end horizontal oscillations. Cable tension and shear forces are measured at the top end. Numerical and experimental results are compared with good agreements in most cases but with some differences in a few cases. The differences are due to drag coefficients caused by vortex shedding. In the numerical modeling, non-uniform element length needs to be employed to cope with the sharp variation of tension and shear forces at near top end.

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Numerical Study on Hydraulic Fluid Flows Within Axial Piston Pumps (액셜 피스톤 펌프내 유압유 유동에 대한 수치해석적 연구)

  • Jeong, Jong-Hyun;Kim, Jong-Ki;Suh, Yong Kweon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.34 no.2
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    • pp.129-136
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    • 2010
  • Axial piston pumps have been widely used as power sources for hydraulic systems, but studies on the fluid flow within the pump have been usually performed using 1-D analysis because of the difficulties in considering the fluid compressibility, high-speed revolution, variation of the flow rate, and complicated geometry. The goal of this study was to understand the hydraulic fluid flow within axial piston pumps by using the 3-D numerical method and the process of generating discharge pressure ripples. To improve the convergence and robustness of the simulation model, a grid system was constructed with hexahedron-type grids around the valve plate. Furthermore, we employed an empirical formula to describe the relationship between the oil density and pressure. The CFD (computational fluid dynamics) results compared well with the experimental data.

Determination of Volume Porosity and Permeability of Drainage Layer in Rainwater Drainage System Using 3-D Numerical Method (3차원 수치해석기법을 이용한 우수배수시스템 배수층의 체적공극과 투수도 결정)

  • Yeom, Seong Il;Park, Sung Won;Ahn, Jungkyu
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.8
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    • pp.449-455
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    • 2019
  • The increase in impermeable pavement from recent urbanization has resulted in an increase in surface runoff. The surface runoff has also increased the burden of the existing drainage system. This drainage system has structural limitations in that the catchment area is reduced by the waste particles transported with the surface runoff. In addition, the efficiency of the drainage system is decreased. To overcome these limitations, a new type of drainage system with a drainage layer was developed and applied. In this study, various volume porosity and permeability of the lower drainage layer were simulated using ANSYS CFX, which is a three dimensional computational fluid dynamics program. The results showed that the outlet velocity of the 35% volume porosity was faster than that of the 20% and 50% cases, and there was no relationship between the volume porosity and drainage performance. The permeability of the drainage layer can be determined from the particle size of the material, and a simulation of five conditions showed that 2 mm sand grains are most suitable for workability and usability. This study suggests appropriate values of the volume porosity and particle size of the drainage layer. This consideration can be advantageous for reducing and preventing flood damage.