• Title, Summary, Keyword: Pitching NACA0012 airfoil

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A study for laminar and turbulent boundary layer theory around a Joukowski and NACA-0012 airfoil by CFD (Airfoil 주변에서의 층류 및 난류경계층 이론에 대한 수치해석)

  • Je, Du-Ho;Hwang, Eun-Seong;Lee, Jang-Hyeoung
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.14 no.4
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    • pp.1533-1539
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    • 2013
  • In the present study, we compared the theory with CFD data about the boundary layer thickness, displacement thickness and momentum thickness. According to the freestream velocity, larminar and turbulent is decided and affect to the flow patterns around the airfoil The boundary layer thickness, displacement thickness and momentum thickness affect to the aerodynamic characteristics of the airfoil(e.g. lift, drag and pitching moment). The separation point is affected by varying angle of attack. In the present study, we used the Joukowski airfoil(c=1), and NACA0012 airfoil was used at CFD. The chord Reynolds number is $Re_c$=3,000, 700,000, respectively and the freestream velocity is 0.045, 10 m/s, respectively. In this paper, the data was a good agreement with that of experimental results, so we can analyze the various airfoil models.

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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    • 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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진동하는 익형(NACA0012)의 공력특성 : Re~$8x10^5$, k<0.1

  • Cho, Tae-Hwan;Youn, Sung-Jun;Chang, Beong-Hee
    • Aerospace Engineering and Technology
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    • v.4 no.2
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    • pp.36-41
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    • 2005
  • The aerodynamic characteristics of the oscillating airfoil(NACA0012) were measured by experimental methods by using the airfoil oscillating test rig installed at KARI 1m wind tunnel. The chord of the airfoil is 0.2m and the span is 0.75m. The lift and pitching moments were calculated by integrating the surface pressure measured by strain-gage type pressure sensors. The test condition is like this : the reduced oscillating frequency(k) < 0.1, Re ~ 820,000, Mach < 0.25. The test results were compared with the reference data published by other facilities.

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Unsteady Aerodynamic Characteristics depending on Reduced Frequency for a Pitching NACA0012 Airfoil at Rec=2.3×104

  • Kim, Dong-Ha;Chang, Jo-Won;Sohn, Myong Hwan
    • International Journal of Aeronautical and Space Sciences
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    • v.18 no.1
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    • pp.8-16
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    • 2017
  • Most of small air vehicles with moving wing fly at low Reynolds number condition and the reduced frequency of the moving wing ranges from 0.0 to 1.0. The physical phenomena over the wing dramatically vary with the reduced frequency. This study examines experimentally the effect of the reduced frequency at low Reynolds number. The NACA0012 airfoil performs sinusoidal pitching motion with respect to the quarter chord with the four reduced frequencies of 0.1, 0.2, 0.4 and 0.76 at the Reynolds number $2.3{\times}10^4$. Smoke-wire flow visualization, unsteady surface pressure measurement, and unsteady force calculation are conducted. At the reduced frequency of 0.1 and 0.2, various boundary layer events such as reverse flow, discrete vortices, separation and reattachment change the amplitude and the rotation direction of the unsteady force hysteresis. However, the boundary layer events abruptly disappear at the reduced frequency of 0.4 and 0.76. Especially at the reduced frequency of 0.76, the local variation of the unsteady force with respect to the angle of attack completely vanishes. These results lead us to the conclusion that the unsteady aerodynamic characteristics of the reduced frequency of 0.2 and 0.4 are clearly distinguishable and the unsteady aerodynamic characteristics below the reduced frequency of 0.2 are governed by the boundary layer events.

Computation of Unsteady Flows over an Oscillating airfoil (진동하는 익형을 지나는 비정상 유동에 관한 계산)

  • Yang C. M.;Baek J. H.
    • 한국전산유체공학회:학술대회논문집
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    • pp.125-130
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    • 1999
  • A flowfields around a NACA0012 airfoil pitching about a 1/4 chord and plunging in vertical displacement are analyzed by solving two-dimensional compressible Navier-Stokes equations. A steady solution was solved first as a validation of the code used and the results were compared with experimental data. Then as a unsteady case, the oscillatory airfoil was solved to compare the results with experimental data. Oscillating rate of pitching and plunging motion was set to have analogy and the magnitude of plunging was set using the magnitude of pitching angle of attack. Finally combined pitching and plunging motion was solved to show the effect of 2 different types of oscillating motion of the airfoil.

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Computational Study on Dynamic Characteristics of a Flapped Airfoil (전산해석을 이용한 고양력장치의 동특성 고찰)

  • Lee, Yung-Gyo;Kim, Cheol-Wan
    • 한국전산유체공학회:학술대회논문집
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    • pp.206-209
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    • 2011
  • During landing approach, an airplane could experience dynamic unstable motion by the combination of a gust and elevator control to cancel the disturbances. This situation is dangerous and could lead to a loss of an airplane. In this paper, numerical analysis was used to study the effect of pitch oscillating 2-D high lift devices in a landing condition. Experimental data on a pitching naca0012 airfoil was used for code validation. Dynamic characteristics of an airfoil, single slotted flap for mid-class passenger aircraft were analyzed. Unsteady Navier-Stokes analysis was performed with Spalart-Allmaras turbulence model for separation dominant low speed flow. As a result, flow hysteresis of a flapped airfoil was more complex than that of an oscillating airfoil. So, dynamic analysis of a flap in a landing condition is very important for operational safety.

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Analysis of Unsteady Subsonic Flow Around a High Angle of Attack of the Oscillating Airfoil (진동하는 고 받음각 날개주위의 비정상 아음속 유동해석)

  • Moon, J.S.;Kim, J.S.
    • 한국전산유체공학회:학술대회논문집
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    • pp.434-440
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    • 2011
  • Oscillating airfoil haw been challenged for the dynamic stalls of airfoil am wind turbines at high angle of attach. Especially, the pressure oscillation has a huge effect on noise generation, structure damage, aerodynamic performance am safety, because the flow has strong unsteadiness at high angle of attack. In this paper, the unsteady aerodynamics coefficients were analyzed for the oscillating airfoil at high angle of attack 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 0.2 and Reynolds number of $1.2{\times}10^4$. The lift, drag, pressure distribution, etc. are analyzed according to the pitching oscillation. Unsteady velocity field, periodic vortex shedding, the unsteady pressure distribution, 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.