• International Journal of Aeronautical and Space Sciences
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• 제18권1호
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• pp.1-7
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• 2017

To predict the transonic buffet onset for a supercritical airfoil with shock-boundary layer interactions, a practical steady approach has been proposed. In this study, it is assumed that the airfoil flow is steady even when buffet onset occurs. Steady Navier-Stokes computations are performed on the supercritical airfoil. Using the aerodynamic parameters calculated from Navier-Stokes solver, various steady approaches for predicting buffet onset are discussed. Among the various steady approaches considered in this study, Thomas' criterion based on Navier-Stokes computation has shown to be the most appropriate indicator of identifying the buffet onset for a supercritical airfoil with shock-boundary layer interactions. Good agreements have been obtained compared with the results of unsteady transonic wind tunnel tests. The present method is shown to be reliable and useful for transonic buffet onset for a supercritical airfoil with shock-boundary layer interactions in terms of practical engineering viewpoint.

• International Journal of Aeronautical and Space Sciences
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• 제9권2호
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• pp.34-40
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• 2008

The aeroelastic analyses for several wing models were performed using the transonic small-disturbance (TSD) equation, which is very efficient, to consider the aerodynamic nonlinearities in the transonic region. For more accurate aerodynamic analysis of airfoil and wing models with shock waves, the viscous equations based on the Green's lag-entrainment equation of boundary-layer effects were coupled with the TSD equation in the transonic region. Finally the aeroelastic characteristics of wing models were investigated through comparisons of the aeroelastic analysis results for wing models considering the change of a thickness of the airfoil section. Moreover, the results of the aeroelastic analysis using the coupled TSD equation with the viscous equations were compared with those using the TSD equation for several wing models.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1998년도 춘계 학술대회논문집
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• pp.61-66
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• 1998

An inverse method for the subsonic and transonic airfoil design was developed using the Euler equations. Two testcases were performed. One was a design of the supercritical airfoil, aiming to be used for the Korean mid-sized (100 passengers class) transport aircraft. The other was the design of an airfoil showing a good cruising performance (L/D ratio) in the high subsonic/transonic flow regimes. These testcases demonstrated the efficiency and the robustness of the developed method.

• 한국전산유체공학회지
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• 제17권4호
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• pp.93-102
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• 2012

Once the condensation of water vapor in moist air around a thin airfoil occurs, liquid droplets nucleate. The condensation process releases heat to the surrounding gaseous components of moist air and significantly affects their thermodynamic and flow properties. As a results, variations in the aerodynamic performance of airfoils can be found. In the present work, the effects of upstream Mach number and thickness ratio of airfoil on the transonic flow of moist air around a thin airfoil are investigated by numerical analysis. The results shows that a significant condensation occurs as the upstream Mach number is increased at the fixed thickness ratio of airfoil($\epsilon$=0.12) and as the thickness ratio of airfoil is increased at the fixed upstream Mach number($M_{\infty}$=0.80). The condensate mass fraction is also increased and dispersed widely around an airfoil as the upstream Mach number and thickness ratio of airfoil are increased. The position of shock wave for moist air flow move toward the leading edge of airfoil when it is compared with the position of shock wave for dry air.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 춘계 학술대회논문집
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• pp.42-48
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• 2004

Numerical simulation of viscous compressible flow in turbomachinery cascade involves many problems due to the complex geometry of blade but also flow phenomena. In the present study, numerical investigations have been performed to examine the three-dimensional flow characteristics inside the transonic linear turbine cascades using a commercial code, FLUENT. Multi-block H-type grids are applied to the high-turning turbine rotor blades and comparisons with the experimental data and the numerical results have been done. In addition, the effects of turbulence models on the prediction of the endwall flows are analyzed in the sense of the flow compressibility.

• 한국항공우주학회지
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• 제30권8호
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• pp.21-29
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• 2002

본 연구는 다공벽과 공동을 사용한 피동제어법을 천음속 습공기 유동에서 발생하는 충격파와 경계층 간섭에 적응하였다. 지배방정식은 액적성장 방정식과 완전히 결합된 2차원, 비정상, 압축성 Navier-Stokes 방정식이며, 3차 오더 MUSCL 타입의 TVD 기법을 사용하였다. 또 난류모델로는 Baldwin-Lomax 모델을 적용하였다. 본 연구에서 적용한 제어법의 유용성을 조사하기 위해 유동의 전압손실과 충격파 변위의 시간의존성 거동을 해석하였다. 수치계산 결과로부터 본 연구의 피동제어기법을 통해 천음속 습공기 유동에서 발생하는 충격파/경계층 간섭으로 인한 전압손실이 상당히 감소하였고, 익에서 충격파 운동을 억제하는 것으로 나타났다. 또 다공영역의 위치가 본 연구의 제어법의 효과에 상당한 영향을 준다는 것이 발견하였다.

• 한국항공우주학회지
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• 제33권11호
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• pp.65-73
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• 2005

천음속 미교란 모델과 1단계 1차 Arrhenius 화학반응식을 이용하여 반응유체의 압축성 유동에 대하여 연구하였다. 유체 유동은 적은 열방출을 수반하는 희박 예혼합 반응에 국한시켰다. 천음속 연소에 끼치는 채널형상과 채널입구 마하수의 영향 등을 수치해석을 이용하여 조사하였다. 수치결과에서 채널확대는 주어진 채널길이 내에서 화학반응을 증가시키고 있음에 반하여 채널수축은 출구 근처에서 화학반응을 억제시키고 있음을 보여주고 있다. 확대형 채널 내에서 입구유동 마하수 증가는 고정된 반응속도에서 유동을 가속시켰으며 불활성 유체 경우에는 나타나지 않는 약한 충격파가 나타났다. 또한 확대형 채널 출구 근처의 압력과 온도를 증가시키고 주어진 채널길이 내에서 반응체의 소비를 도와준다.

• International Journal of Aeronautical and Space Sciences
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• 제18권4호
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• pp.614-622
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• 2017

The characteristics of aerodynamic drag for Transonic Vehicle in Evacuated Tube was investigated using computational fluid dynamics. At first, parametric study on the system was performed according to the Mach number of the vehicle's speed ($Mach_v$), evacuated pressure of the tube ($Pre_t$), and blockage ratio (BR) between the vehicle and tube via axisymmetric flow analysis; the $Mach_v$ ranged from 0.3 to 1.0. The $Pre_t$ was 100, 1,000 and 10,000 Pa and the BR was 0.1, 0.2, and 0.4. In the calculations, the aerodynamic drag of the vehicle was larger when the BR and the pressure became larger. Concerning the $Mach_v$, the drag coefficient ($C_d$) became the maximum when the $Mach_v$ was near the Kantrowitz limit and decreased, which showed the typical transonic flow pattern. Then, three dimensional flow analysis was performed by changing the $Mach_v$ from 0.3 to 1.0 and setting the BR and the $Pre_t$ as 0.34 and 100 Pa, respectively by referring the Hyperloop Alpha documentation. From the calculations, the $C_d$ from three dimensional flow simulations were somewhat larger than those of axisymmetric ones because of the eccentricity of the vehicle inside the tube. However, the pattern of $C_d$ according to the $Mach_v$ was compatible with that of axisymmetric ones.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1998년도 춘계 학술대회논문집
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• pp.29-34
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• 1998

An efficient 3-dimensional compressible solver is developed using the second-order upwind TVD scheme and the multigrid diagonalized ADI method. The multigrid method is improved so that the present DADI algorithm obtains better convergence rates. Results are computed on Cray C90 computer for transonic unsaperated flows past ONERA-M6 wing to demonstrate the accuracy and efficiency. The results show good agreement with experimetal data. A reduction of four orders of residual for 3-dimensional transonic flow is obtained about 99 seconds.

• 한국추진공학회지
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• 제5권2호
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• pp.8-15
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• 2001

터보기계의 효율 향상을 위한 끊임없는 노력에서 익형 형상 설계는 대단히 중요한 부분을 차지하고 있다. 이와 관련하여 천음속 풍동에서 층류 및 난류 경계층 거동(충격파-경계층 상호작용)에 대한 실험적 연구가 CTA 열전대 측정을 통해 이루어졌다. 압축기 익형에 부착된 열전대 실험 결과는 유동의 복잡성에 기인하는 신호의 불명확성 때문에 해석이 대단히 어려운 점이 있으므로 설계자에게 열전대 신호 특성에 대한 정확한 정보를 주기 위해서 다른 측정장치 결과와 비교 분석을 통한 해석기법 이 개발되었다.