• Title/Summary/Keyword: Flow-3D Model

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3-D Concrete Model Using Non-associated Flow Rule in Dilatant-Softening Region of Multi-axial Stress State (3차원 솔리드요소 및 비상관 소성흐름 법칙을 이용한 콘크리트의 응력해석)

  • Seong, Dae Jeong;Choi, Jung Ho
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.12 no.2
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    • pp.193-200
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    • 2008
  • Cohesive and frictional materials such as concrete and soil are pressure dependent. In general, failure criterion for such materials inclined with respect to positive hydrostatic axis in Haigh-Westergaard stress space. Consequently, inelastic volumetric strain always positive with associated flow rule. In this study, to overcome this shortcoming, non-associated flow rule which controls volumetric component of plastic flow is adopted. Numerical analysis based on a constitutive model using nonuniform hardening plasticity with five parameter failure criterion and non-associated flow rule has conducted to predict concrete behavior under multi-axial stress state and verified with experimental result.

Evaluation of turbulence models in rough-wall boundary layers for hydroelectric applications

  • Dutta, Rabijit;Nicolle, Jonathan;Giroux, Anne-Marie;Piomelli, Ugo
    • International Journal of Fluid Machinery and Systems
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    • v.10 no.3
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    • pp.227-239
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    • 2017
  • The accuracy of turbulence models for the Reynolds-Averaged Navier-Stokes (RANS) equations in rough-wall flows is evaluated using data from large-eddy simulations (LES) of boundary layers with favourable and adverse pressure gradients. Some features of the flow (such as flow reversal in the roughness sublayer) cannot be captured accurately by any model, due to the fundamental model formulation. In mild pressure gradients most RANS models are sufficiently accurate for engineering applications, but if strong favourable or adverse pressure gradients are applied (especially those leading to separation) the model performance rapidly degrades.

Analysis of Hydraulic effect on Removing Side Overflow Type Structures in Woo Ee Stream Basin (우이천 유역의 횡단 월류형 구조물 철거에 의한 수리영향 분석)

  • Moon, Young-Il;Yoon, Sun-Kwon;Chun, Si-Young;Kim, Jong-Suk
    • 한국방재학회:학술대회논문집
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    • 2008.02a
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    • pp.687-690
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    • 2008
  • Currently, Stream flow analysis has been accomplished by one or two dimensional equations and was applied by simple momentum equations and fixed energy conservations which contain many reach uppermost limit. In this study, FLOW-3D using CFD(Computational Fluid Dynamics) was applied to stream flow analysis which can solve three dimensional RANS(Reynolds Averaged Navier-Stokes Equation) control equation to find out physical behavior and the effect of hydraulic structures. Numerical simulation accomplished those results was compared by using turbulence models such as $k-\varepsilon$, RNG(Renomalized Group Theory) $k-\varepsilon$ and LES(Large Eddy Simulation). Numerical analysis results have been illustrated by the turbulence energy effects, velocity of flow, water level pressure and eddy flows around the side overflow type structures at Jangwall bridge in urban stream.

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Numerical Analysis on Flow of Cement Paste using 2D-CFD (2차원 CFD를 활용한 시멘트 페이스트의 슬럼프 유동 모사)

  • Yun, Taeyoung
    • International Journal of Highway Engineering
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    • v.19 no.4
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    • pp.19-25
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    • 2017
  • PURPOSES : In this paper, the flow of construction material was simulated using computational fluid dynamics in a 2D axisymmetric condition to evaluate the effect of initial or varying material properties on the final shape of a specimen. METHODS : The CFD model was verified by using a well-known analytical solution for a given test condition followed by performing a sensitivity analysis to evaluate the effect of material properties on the final shape of material. Varying dynamic viscosity and yield stress were also considered. RESULTS : The CFD model in a 2D axisymmetric condition agreed with the analytical solution for most yield stress conditions. Minor disagreements observed at high yield stress conditions indicate improper application of the pure shear assumption for the given material behavior. It was also observed that the variation of yield stress and dynamic viscosity during curing had a meaningful effect on the final shape of the specimen. CONCLUSIONS : It is concluded that CFD modeling in a 2D axisymmetric condition is good enough to evaluate fluidal characteristics of material. The model is able to consider varying yield stress and viscosity during curing. The 3D CFD-DEM coupled model may be required to consider the interaction of aggregates in fluid.

Numerical analysis of the 3D fluid-structure interaction in the sac of artificial heart (인공심장 sac내의 3차원 유체-구조물 상호작용에 대한 수치적 연구)

  • Park M. S.;Shim E. B.;Ko H. J.;Park C. Y.;Min B. G.
    • 한국전산유체공학회:학술대회논문집
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    • 2000.05a
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    • pp.27-32
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    • 2000
  • In this study, the three-dimensional blood flow within the sac of KTAH(Korean artificial heart) is simulated using fluid-structure interaction model. The numerical method employed in this study is the finite element commercial package ADINA. The thrombus formation is one of the most critical problems in KTAH. High fluid shear stress or stagnated flow are believed to be the main causes of these disastrous phenomenon. We solved the fluid-structure interaction between the 3D blood flow in the sac and the surrounding sac material. The sac material is assumed as linear elastic material and the blood as incompressible viscous fluid. Numerical solutions show that high shear stress region and stagnated flow are found near the upper part of the sac and near the comer of the outlet during diastole stage.

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Control of the flow past a sphere in a turbulent boundary layer using O-ring

  • Okbaz, Abdulkerim;Ozgoren, Muammer;Canpolat, Cetin;Sahin, Besir;Akilli, Huseyin
    • Wind and Structures
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    • v.35 no.1
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    • pp.1-20
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    • 2022
  • This research work presents an experimental study's outcomes to reveal the impact of an O-ring on the flow control over a sphere placed in a turbulent boundary layer. The investigation is performed quantitatively and qualitatively using particle image velocimetry (PIV) and dye visualization. The sphere model having a diamater of 42.5 mm is located in a turbulent boundary layer flow over a smooth plate for gap ratios of 0≤G/D≤1.5 at Reynolds number of 5 × 103. Flow characteristics, including patterns of instantaneous vorticity, streaklines, time-averaged streamlines, velocity vectors, velocity fluctuations, Reynolds stress correlations, and turbulence kinetic energy (), are compared and discussed for a naked sphere and spheres having O-rings. The boundary layer velocity gradient and proximity of the sphere to the flat plate profoundly influence the flow dynamics. At proximity ratios of G/D=0.1 and 0.25, a wall jet is formed between lower side of the sphere and flat plate, and velocity fluctuations increase in regions close to the wall. At G/D=0.25, the jet flow also induces local flow separations on the flat plate. At higher proximity ratios, the velocity gradient of the boundary layer causes asymmetries in the mean flow characteristics and turbulence values in the wake region. It is observed that the O-ring with various placement angles (𝜃) on the sphere has a considerable alteration in the flow structure and turbulence statistics on the wake. At lower placement angles, where the O-ring is closer to the forward stagnation point of the sphere, the flow control performance of the O-ring is limited; however, its impact on the flow separation becomes pronounced as it is moved away from the forward stagnation point. At G/D=1.50 for O-ring diameters of 4.7 (2 mm) and 7 (3 mm) percent of the sphere diameter, the -ring exhibits remarkable flow control at 𝜃=50° and 𝜃=55° before laminar flow separation occurrence on the sphere surface, respectively. This conclusion is yielded from narrowed wakes and reductions in turbulence statistics compared to the naked sphere model. The O-ring with a diameter of 3 mm and placement angle of 50° exhibits the most effective flow control. It decreases, in sequence, streamwise velocity fluctuations and length of wake recovery region by 45% and 40%, respectively, which can be evaluated as source of decrement in drag force.

Comparison of Correlation Coefficients and Intraclass Correlation Coefficients Between Two-way FSI Flow Velocity of Simulated Abdominal Aorta and Human 4D Flow MRI Flow Velocity (시뮬레이션 복부 대동맥의 양방향 FSI 유속과 인체 4D flow MRI 유속의 상관계수, 급내상관계수 비교)

  • Ahn, Hae Nam;Kim, Jung Hun;Park, Ji eun;Choi, Hyeun Woo;Lee, Jong Min
    • Journal of Biomedical Engineering Research
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    • v.42 no.4
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    • pp.143-149
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    • 2021
  • In order to predict and prevent the disease of the abdominal aorta, which is the largest artery in the human body and the most common aneurysm, the normal arterial blood flow operation should be considered. To this end, we are trying to solve problems that may arise in the future by executing FSI based on the data obtained from 4D flow MRI. However, to match the similarity between the 4D flow MRI flow and the FSI flow, correlation was used in previous papers, but the correlation did not show the degree of agreement. Therefore, in this paper, we analyzed the correlation between the 4D flow MRI flow velocity of the human abdominal aorta and the two-way FSI flow velocity in which the three physical properties used for the aortic FSI were added to the CT abdominal aorta 3D model and the interclass correlation coefficient. As a result, the physical property M2 showed the highest similarity in correlation and intraclass correlation coefficient, and this property is intended to be helpful in the future study of the abdominal aortic two-way FSI flow rate.

Validation of Aero and Aero-Acoustics simulation for HAWT Model through LBM based technology

  • Senthooran, Sivapalan;Kandasamy, Satheesh;Balasubramanian, Ganapathi
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2010.05a
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    • pp.340-341
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    • 2010
  • A computational study to capture the flow around a floor mounted greenhouse shaped HAWT model was performed using the commercial software PowerFLOW 4.2b. The simulation kernel of this software is based on the numerical scheme known as the Lattice Boltzmann Method (LBM), combined with an RNG turbulence model. Simulations were performed at 60 and 140 km/h free stream air speeds. Selective results from these computational simulations are presented to show the capability of this numerical approach to predict the aerodynamics and aeroacoustics characteristics of the 3-D flow field around the HAWT model.

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Analysis of the Discharge Capacity Improvement of a Lock Gate by Using 3-Dimensional Numerical Simulation (3차원 수치모의를 이용한 배수갑문의 방류능력 개선효과 분석)

  • Kim, Nam-Il;Kim, Dae-Geun;Lee, Kil-Seong;Kim, Dal-Sun
    • Journal of Korea Water Resources Association
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    • v.38 no.3 s.152
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    • pp.189-198
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    • 2005
  • This study showed that numerical simulation can be effectively used to analyze discharge capacity according to the form and arrangement of the lock gate of a tidal power plant. For the numerical simulation, FLOW-3D with Reynolds-averaged Navier-Stokes equation as a governing equation was used. This study found that improvement of apron length and approach angle of guide wall of the lock gate causes differences in discharge capacity of $10\%$ or more. In addition, there was a difference of discharge capacity caused by the connecting structures of the drainage gate and hydraulic turbine structure and the side slope at the end of apron. This study also showed that hydraulic investigation to enhance a discharge capacity is needed when the lock gate is designed and that numerical model experiments can be a useful analysis tool to design the drainage structure, as well as the hydraulic model experiment.

Incompressible Viscous Flow Analysis around a High-Speed Train Including Cross-Wind Effects (측풍영향을 고려한 고속전철 주위의 비압축성 점성 유동 해석)

  • Jung Y. R.;Park W. G.;Kim H. W.;Ha S. D.
    • 한국전산유체공학회:학술대회논문집
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    • 1995.10a
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    • pp.55-63
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    • 1995
  • The flow field around a high-speed train including cross-wind effects has been simulated. This study solves 3-D unsteady incompressible Navier-Stokes equations in the inertial frame using the iterative time marching scheme. The governing equations are differenced with 1st-order accurate backward difference scheme for the time derivatives, 3th-order accurate QUICK scheme for the convective terms and 2nd-order accurate central difference scheme for the viscous terms. The Marker-and-Cell concept was applied to efficiently solve continuity equation, which is differenced with 2nd-order accurate central difference scheme. The 4th-order artificial damping is added to the continuity equation for numerical stability. A C-H type of elliptic grid system is generated around a high-speed train including ground. The Baldwin-Lomax turbulent model was implemented to simulate the turbulent flows. To validate the present procedure, the flow around a high speed train at constant yaw angle of $45^{\circ}\;and\;90^{\circ}$ has been simulated. The simulation shows 3-D vortex generation in the lee corner. The flow separation is also observed around the rear of the train. It has concluded that the results of present study properly agree with physical flow phenomena.

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