• The KSFM Journal of Fluid Machinery
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• v.17 no.5
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• pp.78-82
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• 2014

This paper describes a brief aerodynamic design procedure of multi-stage axial turbine. The design procedure was established including one dimensional scratch design, through flow analysis with empirical correlations, two dimensional airfoil design and three dimensional airfoil stacking. Detailed aerodynamic performance assessment was done with full three dimensional CFD method at the design and off design conditions to construct turbine performance map. With the present method, aerodynamic design procedure of 1st and 2nd stages of high pressure turbine for 10,000lbf class turbofan engine was introduced.

• Journal of computational fluids engineering
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• v.4 no.1
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• pp.53-61
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• 1999

Two-dimensional, unsteady, incompressible and compressible Navier-Stokes codes are developed for the computation of the viscous turbulent flow over high-lift airfoils. The compressible code involves a conventional upwind-differenced scheme for the convective terms and LU-SGS scheme for temporal integration. The incompressible code with pseudo-compressibility method also adopts the same schemes as the compressible code. Three two-equation turbulence models are evaluated by computing the flow over single and multi-element airfoils. The compressible and incompressible codes are validated by predicting the flow around the RAE 2822 transonic airfoil and the NACA 4412 airfoil, respectively. In addition, both the incompressible and compressible code are used to compute the flow over the NLR 7301 airfoil with flap to study the compressible effect near the high-loaded leading edge. The grid systems are efficiently generated using Chimera overlapping grid scheme. Overall, the κ-ω SST model shows closer agreement with experiment results, especially in the prediction of adverse pressure gradient region on the suction surfaces of high-lift airfoils.

• Journal of computational fluids engineering
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• v.19 no.4
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• pp.80-85
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• 2014

High-volume low-speed (HVLS) fans are one category of ceiling fan installed in large enclosings such as warehouses, large barns and health clubs in order to generate comfortable air circulation. As a rotary blade, aerodynamic performance of a HVLS fan is predominantly related to its airfoil(s), and the pitch and twist angles. This paper first, investigates the effects of airfoil on the performances of three different HVLS fans with NACA 5414, 6413 and 7415 airfoils. The fans have six untwisted blades with the diameter of 6 m and rotate at 60 RPM. The blades pitch angels are $12^{\circ}$, $12^{\circ}$ and $13^{\circ}$, respectively. The results are presented in the form of the aerodynamic forces and moments, volumetric flow rate and streamlines. Regarding the volumetric flow of air, the results show that the model with NACA 7415 has the best performance. Hence, two other HVLS fans with the same airfoil but, with four and five blades are studied in order to investigate the effects of number of blades. From the point of view of air circulation still the six-bladed fan is the best one; however, the five-bladed fan is more efficient in power consumption.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.449-452
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• 2009

본 연구에서는 소형 플랩을 채용하여 능동하중제어를 이루고자하는 풍력 블레이드의 적용을 염두해 둔 에어포일 설계를 수행하였다. 블레이드 팁 부분에 플랩을 적용하고자 하는 경우 플랩의 구동장치, 연결 부위 등의 장치 설치를 위한 공간이 블레이드 내부에 필요하다. 이를 위하여 기존의 에어포일의 성능을 유지하면서 뒷전의 두께비가 증가된 에어포일 형상의 설계가 필요하다. 최적설계를 위하여는 MIGA(Multi- Island Genetic Algorithm)을 채용하였으며 에어포일의 성능 계산을 위하여는 Xfoil을 결합하였다. 또한 형상 생성을 위하여 Hick-Henne 형상 함수를 이용하였다. 위와 같은 방법으로 설계된 에어포일은 코드길이 85% 위치에서 두께비 6.3%,양항비 133을 가지게 되어 기본으로 설정한 DU180 에어포일에 비해 성능과 필요 두께비를 모두 능가하는 에어포일이 되었다.

• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.623-626
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• 2015

본 연구에서는 CFD 해석 프로그램 EDISON_CFD를 통하여 2차 세계 대전에 소련에서 제작한 복엽기 AN-2의 기체를 기본 모델로 하여 설제 기체에 사용된 TSAGI P-II-14 airfoil를 이용, 기본 모델의 상단 주익과 미익은 고정하고 하단 주 날개의 위치를 변화시켜 공력특성을 분석하였다. 익형의 평행배치의 경우 기본모델에 비해 양력은 적은 크기로 증가하나 항력이 급격히 증가하여 가장 양항비가 낮은 비효율적인 공력 해석 결과를 보였고 복염기 하단 주익의 돌출은 상단 주익의 돌출에 비해 미세한 양력 감소와 항력 증가를 보여 양항비가 감소하는 현상을 보였다. 상, 하단 주익의 상하 간격이 커질수록 양력은 중가, 항력은 감소하며 간격이 작아질수록 양력의 감소와 항력의 증가를 보였다. 본 연구 해석 결과에 따라 순항조건에서의 익형은 상,하 주익간 수직 간격을 넓게 배치하는 것이 가장 효율적으로 볼 수 있다.

• Journal of Ocean Engineering and Technology
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• v.21 no.3 s.76
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• pp.16-25
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• 2007

A comparative study on the turbulent flaw simulation and the potential flaw analysis has been performed. A law Mach number preconditioned Navier-Stokes solver, using the multi-block grid method and a panel method based on the velocity potential, have been developed and validated by comparison to the experimental data. The present numerical analysis methods are applied to the ground effect problem around the NACA 4412 airfoil. It has been confirmed that the potential flaw analysis on the ground effect, using the image method, is consistent, to some degree, with the viscous calculations for high Reynolds number flows.

• 한국전산유체공학회:학술대회논문집
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• 1999.05a
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• pp.186-191
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• 1999

An Euler solver is developed to predict accurate aerodynamic data such as lift coefficient, drag coefficient, and moment coefficient. The conservation law form of the compressible Euler equations are used in the generalized curvilinear coordinates system. The Euler solver uses a finite volume method and the second order Roe's flux difference splitting scheme with min-mod flux limiter to calculate the fluxes accurately. An implicit scheme which includes the boundary conditions is implemented to accelerate the convergence rate. The multi-block grid is integrated into the flow solver for complex geometry. The flowfields are analyzed around NACA 0012 airfoil in the cases of $M_{\infty}=0.75,\;\alpha=2.0\;and\;M_{\infty}=0.80,\;\alpha=1.25$. The numerical results are compared with other numerical results from the literature. The final goal of this research is to prepare a robust and an efficient Navier-Stokes solver eventually.

• New & Renewable Energy
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• v.5 no.4
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• pp.29-32
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• 2009

본 연구에서는 소형 플랩을 채용하여 능동하중제어를 이루고자하는 풍력블레이드의 적용을 염두해 둔 에어포일 설계를 수행하였다. 블레이드 팁 부분에 플랩을 적용하고자 하는 경우 플랩의 구동 장치, 연결 부위 등의 장치 설치를 위한 공간이 블레이드 내부에 필요하다. 이를 위하여 기존의 에어포일의 성능을 유지하면서 뒷전의 두께비가 증가된 에어포일 형상의 설계가 필요하다. 최적설계를 위하여는 MIGA(Multi-Island Genetic Algorithm)을 채용하였으며 에어포일의 성능 계산을 위하여는 Xfoil을 결합하였다. 또한 형상 생성을 위하여 Hick-Henne 형상 함수를 이용하였다. 위와 같은 방법으로 설계된 에어포일은 코드길이 85% 위치에서 두께비 6.3%,양항비 133을 가지게 되어 기본으로 설정한 DU180에어포일에 비해 성능과 필요 두께비를 모두 능가하는 에어포일이 되었다.

• International Journal of Aeronautical and Space Sciences
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• v.7 no.1
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• pp.1-12
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• 2006

In this study, a surrogate model is applied to multi-objective aerodynamic optimization design. For the balanced exploration and exploitation, each objective function is converted into the Expected Improvement (EI) and this value is used as fitness value in the multi-objective optimization instead of the objective function itself. Among the non-dominated solutions about EIs, additional sample points for the update of the Kriging model are selected. The present method was applied to a transonic airfoil design. Design results showed the validity of the present method. In order to obtain the information about design space, two data mining techniques are applied to design results: Analysis of Variance (ANOVA) and the Self-Organizing Map (SOM).

• Journal of computational fluids engineering
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• v.12 no.4
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• pp.28-37
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• 2007

In this study, a multi-block structured grid deformation code based on a hybrid of a transfinite interpolation algorithm and spring analogy was developed. The configuration was modeled by a Bezier surface. A combination of the spring analogy for block vertices and the transfinite interpolation for interior grid points helps to increase the robustness and makes it suitable for distributed computing. An elliptic smoothing operator was applied to the block faces with sub-faces in order to maintain the grid smoothness and skewness. The capability of this code was demonstrated on a range of simple and complex configurations including an airfoil and a wing-body configuration.