• Wind and Structures
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• 제31권4호
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• pp.373-380
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• 2020

For large-scale 5MW offshore wind turbines, the discrete equation of fluid domain and the motion equation of structural domain with geometric nonlinearity were built, the three-dimensional modeling of the blade considering fluid-structure interaction (FSI) was achieved by using Unigraphics (UG) and Geometry modules, and the numerical simulation and the analysis of the vibration characteristics for wind turbine structure under rotating effect were carried out based on ANSYS software. The results indicate that the rotating effect has an apparent effect on displacement and Von Mises stress, and the response and the distribution of displacement and Von Mises stress for the blade in direction of wingspan increase nonlinearly with the equal increase of rotational speeds. Compared with the single blade model, the blade vibration period of the whole machine model is much longer. The structural coupling effect reduces the response peak value of the blade displacement and Von Mises stress, and the increase of rotational speed enhances this coupling effect. The maximum displacement difference between two models decreases first and then increases along wingspan direction, the trend is more visible with the equal increase of rotational speed, and the boundary point with zero displacement difference moves towards the blade root. Furthermore, the Von Mises stress difference increases gradually with the increase of rotational speed and decreases nonlinearly from the blade middle to both sides. The results can provide technical reference for the safe operation and optimal design of offshore wind turbines.

• 한국항공우주학회지
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• 제34권1호
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• pp.24-31
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• 2006

본 연구에서는 완전 내재적 기법을 이용한 2계 자유도 모델에 대한 플러터 해석을 수행하였다. 유동해석을 위하여 2차원 Navier-Stokes 지배방정식을 ε-SST 난류모델과 DP-SGS 병렬화 기법을 이용해 구성하였다. 구조해석을 위하여 피치 와 플런지의 2계 자유도를 갖는 모델을 구성하였으며 시간영역에서의 해석을 위하여 유동해석과 마찬가지로 이중 시간 전진 기법을 이용하였다. 가상 시간 전진에서 유체-구조 결합을 통해서 강성결합을 구현하였으며 이를 천음속 플러터 예측에 적용하였다. 플러터 해석의 전형적인 응답인 감쇠응답, 중립응답, 발산응답 및 limit cycle oscillation (LCO) 등을 계산하였으며, 더불어 플러터 속도 경계곡선을 작성하였다. 천음속 플러터 해석은 난류모델 뿐만 아니라 유체-구조 결합 방법에 따라 다른 특성을 보임을 확인하였다.

• 한국전산유체공학회지
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• 제13권4호
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• pp.86-95
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• 2008

For analyses of multi-phase flows in a water-cooled nuclear power plant, a three-dimensional SIMPLE-algorithm based hydrodynamic solver CUPID-S has been developed. As governing equations, it adopts a two-fluid three-field model for the two-phase flows. The three fields represent a continuous liquid, a dispersed droplets, and a vapour field. The governing equations are discretized by a finite volume method on an unstructured grid to handle the geometrical complexity of the nuclear reactors. The phasic momentum equations are coupled and solved with a sparse block Gauss-Seidel matrix solver to increase a numerical stability. The pressure correction equation derived by summing the phasic volume fraction equations is applied on the unstructured mesh in the context of a cell-centered co-located scheme. This paper presents the numerical method and the preliminary results of the calculations.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.71-78
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• 2008

For analyses of multi-phase flows in a water-cooled nuclear power plant, a three-dimensional SIMPLE-algorithm based hydrodynamic solver CUPID-S has been developed. As governing equations, it adopts a two-fluid three-field model for the two-phase flows. The three fields represent a continuous liquid, a dispersed droplets, and a vapour field. The governing equations are discretized by a finite volume method on an unstructured grid to handle the geometrical complexity of the nuclear reactors. The phasic momentum equations are coupled and solved with a sparse block Gauss-Seidel matrix solver to increase a numerical stability. The pressure correction equation derived by summing the phasic volume fraction equations is applied on the unstructured mesh in the context of a cell-centered co-located scheme. This paper presents the numerical method and the preliminary results of the calculations.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년 추계학술대회논문집
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• pp.71-78
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• 2008

For analyses of multi-phase flows in a water-cooled nuclear power plant, a three-dimensional SIMPLE-algorithm based hydrodynamic solver CUPID-S has been developed. As governing equations, it adopts a two-fluid three-field model for the two-phase flows. The three fields represent a continuous liquid, a dispersed droplets, and a vapour field. The governing equations are discretized by a finite volume method on an unstructured grid to handle the geometrical complexity of the nuclear reactors. The phasic momentum equations are coupled and solved with a sparse block Gauss-Seidel matrix solver to increase a numerical stability. The pressure correction equation derived by summing the phasic volume fraction equations is applied on the unstructured mesh in the context of a cell-centered co-located scheme. This paper presents the numerical method and the preliminary results of the calculations.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2951-2954
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• 2007

Tumor hemodynamics in vascular state is numerically simulated using pressure node solution. The tumor angiogenesis pattern in our previous study is used for the geometry of vessel networks. For tumor angiogenesis, the equation that governed angiogenesis comprises a tumor angiogenesis factor (TAF) conservation equation in time and space, which is solved numerically using the Galerkin finite element method. A stochastic process model is used to simulate vessel formation and vessel. In this study, we use a two-dimensional model with planar vessel structure. Hemodynamics in vessel is assumed as incompressible steady flow with Newtonian fluid properties. In parent vessel, arterial pressure is assigned as a boundary condition whereas a constant terminal pressure is specified in tumor inside. Kirchhoff's law is applied to each pressure node to simulate the pressure distribution in vessel networks. Transient pressure distribution along with angiogenesis pattern is presented to investigate the effect of tumor growth in tumor hemodynamics.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.209-214
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• 2002

The present study is to compare the performance of turbulence models in the analysis of the complex flowfield of an axial flow compressor. Baldwin-Lomax turbulence model and k-$\omega$ turbulence model were selected for the comparison. The thin-layer Wavier-Stokes equation was calculated by explicit, finite-difference numerical scheme. A spatially-varying time-step and an implicit residual smoothing were used to improve convergence. Experimental measurements for NASA rotor 37 were cited fer the comparison with numerical data. The compared two turbulence models gave similar performance over all except for total pressure.

• Journal of Advanced Marine Engineering and Technology
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• 제15권2호
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• pp.64-72
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• 1991

The unsteady, two-dimensional laminar flow and heat transfer of an incompressible, constant-property fluid flowing around a circular cylinder are numerically analyzed. The Navier-Strokes equation and the energy equation are solved by the finite difference method. The range of the Reynolds number is 10 to 100 and the Prandtl number considered is 0.7. The contours of the flow pattern, equi-vorticity line and isotherm pattern around a circular cylinder are shown. Also, numerical solutions of the surface vorticity, pressure coefficient, drag coefficient, local Nusselt number and mean Nusselt number are obtained. The numerical results for the final time fo calculation are compared with the other available experimental and theoretical results for the steady state and are found to be in good agreement with them.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.487-491
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• 2009

center-body디퓨져에 대한 형상 설계 요소를 분석하고 수치적 기법을 통한 설계형상 변수를 구성하였다. 수치기법으로는 Center-body 디퓨져의 내부유동해석을 위하여 2차원 축대칭 Navier-Stokes equation와 $k-{\omega}$난류모델을 사용하였다. 또한 center-body디퓨져의 시동압력과 진공도 및 형상설계변수에 대해서 2차목 디퓨져와 비교하였다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2001년도 유체기계 연구개발 발표회 논문집
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• pp.76-80
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• 2001

Unsteady compressible Euler equation is solved and the high-order, high-resolution numerical solver, physical boundary condition, adaptive nonlinear artificial dissipation model and conformal mapping are applied to computation of steady transonic flow and unsteady acoustics. The acoustic characteristics of axi-symmetric duct and two dimensional straight/S channel are studied and the computation results shows good agreements with linear analysis. In transonic case, local time stepping and canceling-the-residual techniques are used for convergence acceleration. The aspect of flow and acoustics in S-channel and the Pattern of noise radiation is changed by inflow Mach no. and static pressure at fan-face.