• Title/Summary/Keyword: Transonic flow

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Prediction of Transonic Buffet Onset for a Supercritical Airfoil with Shock-Boundary Layer Interactions Using Navier-Stokes Solver

  • Chung, Injae
    • International Journal of Aeronautical and Space Sciences
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    • v.18 no.1
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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.

Transonic Aeroelastic Analyses of Wings Considering UViscous and Thickness Effects

  • Kim, Jong-Yun;Kim, Kyung-Seok;Lee, In
    • International Journal of Aeronautical and Space Sciences
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    • v.9 no.2
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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.

Subsonic/Transonic Airfoil Design Using an Inverse Method (Inverse 기법을 이용한 아음속/천음속 익형 설계)

  • Lee Jae Woo;Lee Young-Ki;Byun Yung-Hwan
    • 한국전산유체공학회:학술대회논문집
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    • 1998.05a
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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.

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THE EFFECTS OF MACH NUMBER AND THICKNESS RATIO OF AIRFOIL ON TRANSONIC FLOW OF MOIST AIR AROUND A THIN AIRFOIL WITH LATENT HEAT TRANSFER (잠열 전달이 일어나는 얇은 익형주위의 천음속 습공기 유동에서의 마하수와 익형 두께비의 영향)

  • Lee, J.C.
    • Journal of computational fluids engineering
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    • v.17 no.4
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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.

Numerical Simulation of Three-Dimensional Compressible Viscous Flow Characteristics in Axial-Flow Turbines (축류터빈 내부의 3차원 압축성 점성 유동특성에 관한 수치 시뮬레이션)

  • Chung H. T.;Jung H. N.
    • 한국전산유체공학회:학술대회논문집
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    • 2004.03a
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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.

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Study on the Passive Shock/Boundary Layer Interaction Control in Transonic Moist Air Flow (습공기 유동에서 발생하는 충격파와 경계층 간섭의 피동제어에 관한 연구)

  • Baek, Seung-Cheol;Kwon, Soon-Bum;Kim, Heuy-Dong
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.8
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    • pp.21-29
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    • 2002
  • In the present study, a passive control method, using a porous wall and cavity system, is applied to the shock wave/boundary layer interactions in transonic moist air flow. The two-dimensional, unsteady, compressible, Navier-Stokes equations, which are fully coupled with a droplet growth equation, are solved by the third-order MUSCL type TVD finite difference scheme. Baldwin-Lomax model is employed to close the governing equations. In order to investigate the effectiveness of the present control method, the total pressure loss of the flow and the time-dependent behaviour of shock motions are analyzed in detail. The computed results show that the present passive control method considerably reduces the total pressure losses due to the shock wave/boundary layer interaction in transonic moist air flow and suppresses the unsteady shock wave motions over the airfoil as well. It is also found that the location of the porous ventilation significantly affects the control effectiveness.

A Numerical Study of Channel Shape and Mach Number Effects on Transonic Combustion (채널형상과 마하수가 천음속 연소에 미치는 영향에 대한 수치해석적 연구)

  • Lee, Jang-Chang
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.33 no.11
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    • pp.65-73
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    • 2005
  • The compressible flow of reactive fluid is investigated by using the transonic small-disturbance (TSD) model and the one-step first-order Arrhenuis chemical reaction. The fluid flow is restricted to dilute premixed reactions with small heat release. The effects of channel shape and Mach number on transonic combustion are studied by numerical analysis. The results show that the channel divergence increases the chemical reaction within the given channel length whereas the channel convergence inhibits the chemical reaction near the outlet and that increasing the inlet flow Mach number at a fixed reaction rate causes the flow acceleration in a diverging channel and the appearance of weak shock waves which do not show in the inert flow case. It also helps to increase the pressure and temperature near the diverging channel outlet and to consume the reactant within the given channel length.

A Study on the Aerodynamic Drag of Transonic Vehicle in Evacuated Tube Using Computational Fluid Dynamics

  • Kang, Hyungmin;Jin, Yingmei;Kwon, Hyeokbin;Kim, Kyuhong
    • International Journal of Aeronautical and Space Sciences
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    • v.18 no.4
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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.

An Efficient Multigrid Diagonalized ADI Method for 3-Dimensional Compressible Flow Analysis (3차원 압축성 유동 해석을 위한 효율적인 다중 격자 DADI 기법)

  • Park Soo-Hyung;Sung Chun-ho;Kwon Jang Hyuk
    • 한국전산유체공학회:학술대회논문집
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    • 1998.05a
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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.

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An Experimental Study of Compressor Section Profile in Transonic Flow (천음속 유동하의 압축기 익형에 대한 실험적 연구)

  • 류영진
    • Journal of the Korean Society of Propulsion Engineers
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    • v.5 no.2
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    • pp.8-15
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    • 2001
  • In the continuing quest for increased turbomachinery efficiency, the part played by blade profile shape remains crucial. The application of a heated thin metallic film with CTA(constant temperature anemometer) to the measurements of the laminar and turbulent boundary layer behavior(shock-boundary layer-interaction) in a transonic wind tunnel. Results of measurements with hot-film sensors on transonic compressor blades are extremely difficult to interpret because of ambiguous probe signals due to the complexity of the local flow pattern. In order to get the explicit information and give the designer to interpret characteristic signals from hot-film probes, a method was developed by comparing the results with other measuring technic results.

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