• Title/Summary/Keyword: LES turblent model

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Unsteady Aerodynamic characteristics at High Angle of Attack around Two Dimensional NACA0012 Airfoil (고 받음각 2차원 NACA0012 에어포일 주위의 비정상 공기역학적 특성)

  • Yoo, Jae-Kyeong;Kim, Jae-Soo
    • 한국전산유체공학회:학술대회논문집
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    • 2011.05a
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    • pp.414-419
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    • 2011
  • Missile am fighter aircraft have been challenged by low restoring nose-down pitching moment at high angle of attach. The consequence of weak nose-down pitching moment can be resulting in a deep stall condition. Especially, the pressure oscillation has a huge effect on noise generation, structure damage, aerodynamic performance and safety, because the flow has strong unsteadiness at high angle of attack. In this paper, the unsteady aerodynamics coefficients were analyzed at high angle of attack up to 60 degrees around two dimensional NACA0012 airfoil. The two dimensional unsteady compressible Navier-Stokes equation with a LES turbulent model was calculated by OHOC (Optimized High-Order Compact) scheme. The flow conditions are Mach number of 0.3 and Reynolds number of $10^5$. The lift, drag, pressure distribution, etc. are analyzed according to the angle of attack. The results at a low angle of attack are compared with other results before a stall condition. From a certain high angle of attack, the strong vortex formed by the leading edge are flowing downstream as like Karman vortex around a circular cylinder. Unsteady velocity field, periodic vortex shedding, the unsteady pressure distribution on the airfoil surface, and the acoustic fields are analyzed. The effects of these unsteady characteristics in the aerodynamic coefficients are analyzed.

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ANALYSIS OF UNSTEADY OSCILLATING FLOW AROUND TWO DIMENSIONAL AIRFOIL AT HIGH ANGLE OF ATTACK (고받음각 2차원 에어포일 주위의 비정상 유동의 진동 특성에 관한 연구)

  • Yoo, J.K.;Kim, J.S.
    • Journal of computational fluids engineering
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    • v.18 no.1
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    • pp.1-6
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    • 2013
  • Missile and fighter aircraft have been challenged by low restoring nose-down pitching moment at high angle of attach. The consequence of weak nose-down pitching moment can be resulting in a deep stall condition. Especially, the pressure oscillation has a huge effect on noise generation, structure damage, aerodynamic performance and safety, because the flow has strong unsteadiness at high angle of attack. In this paper, the unsteady aerodynamics coefficients were analyzed at high angle of attack up to 50 degrees around two dimensional NACA0012 airfoil. The two dimensional unsteady compressible Navier-Stokes equation with a LES turbulent model was calculated by OHOC (Optimized High-Order Compact) scheme. The flow conditions are Mach number of 0.3 and Reynolds number of $10^5$. The lift, drag, pressure, entropy distribution, etc. are analyzed according to the angle of attack. The results of average lift coefficients are compared with other results according to the angle of attack. From a certain high angle of attack, the strong vortex formed by the leading edge are flowing downstream as like Karman vortex around a circular cylinder. The primary and secondary oscillating frequencies are analyzed by the effects of these unsteady aerodynamic characteristics.