• 한국유체기계학회 논문집
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• 제17권2호
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• pp.12-23
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• 2014

A parametric study on anti-vortex holes for turbine blade cooling was investigated numerically. Three-dimensional Reynolds-averaged Navier-Stokes equations and shear stress transport turbulence model were used for analysis of anti-vortex film cooling. Validation of numerical results was carried out comparing with experimental data. The cooling performance of anti-vortex holes was assessed by two geometric variables, the ratio of diameters of holes and the lateral distances between the primary hole and anti-vortex hole at blowing ratios of 0.5 and 1.0. The results showed that the spatially-averaged film-cooling effectiveness increases as the ratio of the diameters increases and the distance between the primary hole and anti-vortex hole decreases.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.437-442
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• 2004

The optimization of a blade sweep for a transonic axial compressor rotor (NASA rotor 37) has been performed using a response surface method and a Reynolds-averaged Wavier-Stokes (RANS) flow simulation. Two shape variables of the rotor blade, which are used to define a blade sweep, are introduced to increase an adiabatic efficiency. Data points for response evaluations have been selected by D-optimal design, and linear programming method has been used for an optimization on a response surface. The result shows that the adiabatic efficiency is increased to about 1 percent compared to that of the reference shape of the rotor blade. Relatively high increasement of the adiabatic efficiency is obtained between 20 and 60 percent span. In the present study, backward swept blade is more effective to increase the adiabatic efficiency In the axial compressor rotor.

• 한국유체기계학회 논문집
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• 제18권3호
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• pp.66-73
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• 2015

This paper deals with a parametric study on boot-shaped ribs in a rectangular cooling channel. Numerical analysis of the flow and heat transfer was performed using three-dimensional Reynolds averaged Navier-Stokes equations with the Speziale, Sarkar and Gatski turbulence model. The parametric study was performed for the parameters, tip width-to rib width, tip height-to-rib height, rib height-to-channel height, and rib height-to-width ratios. To assess the cooling performance and friction loss, Numsselt number and friction factor were defined as the performance parameter, respectively. The results showed that the cooling performance and friction loss were seriously affected by the four geometric parameters.

• 한국유체기계학회 논문집
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• 제9권4호
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• pp.36-42
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• 2006

In the present work, characteristics of the flow in the cage of a steam turbine bypass control valve for thermal power plant are investigated. Experimental measurement for wall static pressure has been carried out to validate numerical solutions. And, the flowfield is analyzed by solving steady three-dimensional Reynolds-averaged Navier-Stokes equations. Shear stress transport (SST) model is used as turbulence closure. The effects of the flow area between stages of the cage on the pressure drop are also found.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1999년도 춘계 학술대회논문집
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• pp.171-176
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• 1999

In the present paper, three types of the flow solvers were used to investigate the influence on the airfoil shape optimization. The adopted equations, i.e., Euler , thin layer Navier- Stokes and full Navier-Stokes ones, are solved using implicit LU-ADI decomposition scheme. The feasible direction algorithm with the sinusoidal function was used as an optimization algorithm. The present numerical method was applied to the drag minimization problems under the initial shape of NACA0012 airfoils.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 추계 학술대회논문집
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• pp.152-157
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• 2003

As computer capacity has been progressed continuously, the studies of the flow characteristics have been performing by the numerical methods actively. Recent numerical simulation has a tendency to require the higher-order accuracy in time, as well as in space. This tendency is more true in LES and acoustic noise simulation. In this study, 3-dimensional unsteady Incompressible Navier-Stokes equation was solved by numerical method using the fractional step method with the fourth order compact pade scheme to achieve high accuracy To validate the present code and algorithm, 3D flow-field around a cylinder was simulated. The drag coefficient and lift coefficient were computed and, then, compared with experiment. The present code will be tailored to LES simulation for more accurate turbulent flow analysis.

• 대한기계학회논문집
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• 제16권2호
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• pp.313-324
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• 1992

Two-dimensional Navier-Stokes code has been developed for analysis of turbomachinery blade rows and other internal flows. The Navier-Stokes equations are written in a Cartesian coordinate system, then mapped into a generalized body-fitted coordinate system. All direction of viscous terms are incorporated and turbulent effects are modeled using the Baldwin-Lomax algebraic model. Equation are discretized using finite difference method on the C-type grids and solved using implicit LU-ADI decomposition scheme. Calculations are made at a VKI turbine cascade flow in a transonic wind-tunnel and compared to experimental data. Present numerical scheme is shown to be in good agreement with the previous experimental results and simulates the two-dimensional viscous flow phenomena.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2017년도 학술발표회
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• pp.142-146
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• 2017

지진해일의 수리특성을 분석하기 위하여 유사한 파형특성을 가진 고립파를 많이 이용하고 있다. 그러나 고립파의 근사파형은 실제 지진해일에 비해 상당히 좁은 파형분포를 가지고 있다. 이에 수치모의에서는 기존의 고립파 근사식을 개량하여 고립파형의 지진해일을 수치적으로 생성하고 있다. 본 연구에서는 지진해일의 파형분포에 따른 월파특성을 수치적으로 조사하기 위하여 개량된 고립파 근사식을 2차원 N-S solver에서 적용하였다. 이것에 기초하여 수치파동수조에 직립호안과 그 배후에는 월파수조를 설치하고, 지진해일 월파량을 측정하였다. 수치해석결과로부터 직립호안 주변의 공간파형과 마루 위의 유속분포로부터 파형분포에 따른 월파현상을 분석할 수 있었다. 또한 기존 고립파 근사이론 대비 개량된 고립파의 체적비에 따른 월파량 변화를 정량적으로 조사하였다. 그 결과 지진해일의 체적비가 증가할수록 월파량이 거의 선형적으로 증가하는 경향을 나타내었다.

• 풍력에너지저널
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• 제2권1호
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• pp.61-67
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• 2011

In the present study, numerical unsteady simulations of the NREL Phase VI wind turbine in downwind operation conditions were conducted to investigate rotor-tower interaction. The calculations were performed using an unstructured mesh, incompressible Reynolds-averaged Navier-Stokes flow solver. To capture the unsteady effects associated with the tower shadow between the rotor blades and the tower, the wind turbine was modelled including the rotor, tower, hub, and nacelle. The present results generally showed good agreements with available experimental data. At the lowest wind speed, the pressure distribution was characterized by a complete collapse of the suction peak on the blade when the blade passes through the tower wake. It was found that unsteady effects play a significant role in the response of the blades.

• 한국해안·해양공학회논문집
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• 제32권1호
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• pp.17-25
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• 2020

본 연구에서는 1 MW급 수평축 조류발전기의 출력 및 유동특성을 분석하기 위해 3차원 레이놀즈 평균 나비어-스톡스 해석을 수행하였다. 난류해석을 위해 SST(shear stress transport) 난류모델을 사용하였고, 유동해석을 위한 계산영역은 육면체격자로 구성하였으며, 최적의 격자 크기를 결정하기 위하여 격자 의존성 시험을 수행하였다. 터빈의 노즈 형상 및 유입각도, 그리고 타워 구조물의 영향을 분석하였다. 노즈 형상의 경우 노즈의 직경 대비 축방향 길이의 비가 증가할수록 터빈 출력이 향상되는 결과를 확인할 수 있었고, 유입각도가 약 15° 이상에서는 터빈의 성능이 약 10% 이상 감소하는 것을 확인하였다. 또한 타워 구조물에 의하여 하류식 터빈의 경우 상류식 터빈에 비하여 성능이 1% 감소함을 알 수 있었다.