• 제목/요약/키워드: High Angle of Attack

검색결과 205건 처리시간 0.028초

DESCRIPTIONS OF ATTACK ANGLE AND IDEAL LIFT COEFFICIENT FOR VARIOUS AIRFOIL PROFILES IN WIND TURBINE BLADE

  • JAEGWI GO
    • Journal of the Korean Society for Industrial and Applied Mathematics
    • /
    • 제27권1호
    • /
    • pp.75-86
    • /
    • 2023
  • The angle of attack is highly sensitive to pitch point in the airfoil shape and the decline of pitch point value induces smaller angle of attack, which implies that airfoil profile possessing closer pitch point to the airfoil tip reacts more sensitively to upcoming wind. The method of conformal transformation functions is employed for airfoil profiles and airfoil surfaces are expressed with a trigonometric series form. Attack angle and ideal lift coefficient distributions are investigated for various airfoil profiles in wind turbine blade regarding conformal transformation and pitch point. The conformed angle function representing the surface angle of airfoil shape generates various attack angle distributions depending on the choice of surface angle function. Moreover, ideal attack angle and ideal lift coefficient are susceptible to the choice of airfoil profiles and uniform loading area. High ideal attack angle signifies high pliability to upcoming wind, and high ideal lift coefficient involves high possibility to generate larger electric energy. According to results obtained pitch point, airfoil shape, uniform loading area, and the conformed airfoil surface angle function are crucial factors in the determination of angle of attack.

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

  • 유재경;김재수
    • 한국전산유체공학회지
    • /
    • 제18권1호
    • /
    • pp.1-6
    • /
    • 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.

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

  • 유재경;김재수
    • 한국전산유체공학회:학술대회논문집
    • /
    • 한국전산유체공학회 2011년 춘계학술대회논문집
    • /
    • pp.414-419
    • /
    • 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.

  • PDF

고영각 NACA 0021 익형 주위의 비정상 유동장에 대한 수치해석적 연구 (A Numerical Study on Unsteady Flowfield around a NACA 0021 Airfoil at High Angles of Attack)

  • 김상덕
    • 한국항공운항학회지
    • /
    • 제28권2호
    • /
    • pp.12-17
    • /
    • 2020
  • Even though the benefit of flight at high angle-of-attack is to be able to reduce the speed of flight and maneuvers in complex flight environment, the flight at high angle-of-attack, however, is easy to be in stall which is characterized by sever unsteady flow separation over an airfoil. Current unsteady numerical analysis using DES was conducted to predict the aerodynamic characteristics of a NACA 0021 airfoil at high angle-of-attack conditions. And this provides the comparison with the steady numerical one with the typical turbulence models. The unsteady calculation by DES is appropriate in terms of predicting the aerodynamic performance of NACA 0021 airfoil at high angle-of-attack conditions.

NACA 0021 익형 유동장의 수치해석적 연구 (A Numerical Study on the Flowfield around a NACA 0021 Airfoil at Angles of Attack)

  • 김상덕
    • 한국항공운항학회지
    • /
    • 제24권4호
    • /
    • pp.20-25
    • /
    • 2016
  • A primary benefit of flight at high angle-of-attack conditions is to be able to reduce the speed of flight and maneuvers, which can enhance the capability of sensing and obstacle avoidance for a small UAV. The flight at high angle-of-attack conditions, however, is easy to be beyond stall which is characterized by substantial flow separation over an airfoil. Current numerical analysis was conducted on the capabilities of three representative turbulence models to predict the aerodynamic characteristics of a typical airfoil at angle-of-attack conditions. The investigation shows that these turbulence models provide good comparison with experimental data for attached flow at moderate angle-of-attack conditions. Calculation by current turbulence models are, however, not appropriate at high angle-of-attack conditions with flow separation.

카나드 형상 고시동 항공기 공력설계를 우한 높은 받음각 정적 안정성 분석 실험 연구 (An Experimental Study on High Angle of Attack Static Stability Analysis For the Aerodynamic Design of Canard Type High Maneuver Aircraft)

  • 정인재
    • 한국항공우주학회지
    • /
    • 제35권7호
    • /
    • pp.575-580
    • /
    • 2007
  • 카나드 형상 고기동 항공기의 개념 설계 단계에서 높은 받음각 항공기 정적 안정성 분석을 위해 저속 소형 풍동시험을 수행하였다. 본 연구에서는 1/50축척의 일반적인 카나드-동체-날개 형상을 소형 풍동시험 모델로 사용하였다. 높은 받음각 비선형특성을 포함한 정적 안정성을 분석하기 위하여 카나드 굽힘에 따른 수직 꼬리 날개 효과를 분석하였다. 또한 높은 받음각에서 Nose Chine 효과를 분석하였다. 실험 연구에서 얻은 결과를 토대로 카나드 형상 항공기 높은 받음각 정적 안정성에 미치는 형상 변화 효과를 분석할 수 있었다.

대전차유도무기의 종말 받음각 및 입사각의 상관관계에 의한 표적 파괴율 분석 (Kill Probability Analysis Based on the Relation between Final Angle of Attack and Impact Angle of a Guided Anti-tank Missile)

  • 정동길
    • 한국군사과학기술학회지
    • /
    • 제13권4호
    • /
    • pp.520-527
    • /
    • 2010
  • The kill probability of a missile depends on guidance error, warhead performance, and etc. In this paper, we analyzed the kill probability of anti-tank missile in a new approach. Under the condition that the missile hit the target, we studied the effect of angle of attack and impact angle. High impact angle increase the probability that the missile hits the upper armour which is relatively weaker, while high angle of attack at the impact instant decreases the effectiveness of the jet induced by the warhead. We proposed a way to increase the capability of penetration by analyzing the interrelation between impact angle and angle of attack.

원형 캐비테이터의 받음각에 따른 환기초공동 형상 예측 연구 (The prediction of ventilated supercavitation shapes according to the angle of attack of a circular cavitator)

  • 이종주;김민재;백부근;김경천
    • 한국가시화정보학회지
    • /
    • 제19권3호
    • /
    • pp.22-30
    • /
    • 2021
  • Ventilated cavity shapes by varying angle of attack of a circular cavitator were predicted based on Logvinovich's Independence Principle in order to verify the cavity shape prediction method. The prediction results were compared with model experiments conducted in the high-speed cavitation tunnel. In the prediction of the cavity centerline, the movement of the cavity centerline due to the effect of gravity and cavitator's angle of attack were well predicted. In the prediction of the cavity contour, it was found that the cavity edge prediction error increased as the angle of attack increased. The error of the upper cavity contour was small at the positive angle of attack, and the error of the lower cavity contour was small at the negative angle of attack.

아음속 유동하의 고 받음각 물체 주위의 비대칭 와류 특성 연구 (Asymmetric Vortices around a Body at High Angle of Attack Subsonic Flow)

  • 박미영;김완섭;이재우;박수형
    • 한국전산유체공학회:학술대회논문집
    • /
    • 한국전산유체공학회 2008년도 춘계학술대회논문집
    • /
    • pp.33-38
    • /
    • 2008
  • Numerical investigation of asymmetric vortices at high angles of attack subsonic flow is performed using three-dimensional Navier-Stokes equations. A small bump has been carefully selected and attached near the nose of an ogive cylinder to simulate symmetric vortices. Selected bump shape does develop asymmetric vortices and is verified using Lamont's experimental results. By changing the angle of attack, Reynolds numbers, and Mach numbers, the characteristics of asymmetric vortices are observed. The angle of attack which contributes significantly to the generation of asymmetric vortices are over 30 degrees. By increasing Mach number and Reynolds number asymmetric vortices, hence the side forces show decreasing trend..

  • PDF

고받음각 초음속 유동에서의 세장형 몸체 주변에 발생하는 비대칭와류에 대한 수치적 연구 (The Numerical Analysis of Asymmetric Vortices around the Slender body at High Angle of Attack Supersonic Flow)

  • 전영진;지영무;김기수;서형석;변영환;이재우
    • 한국추진공학회:학술대회논문집
    • /
    • 한국추진공학회 2007년도 제28회 춘계학술대회논문집
    • /
    • pp.335-338
    • /
    • 2007
  • 공대공미사일의 경우 초음속 하에서 고 기동성을 얻기 위하여 고받음각 능력이 요구되어진다. 옆 미끄러짐이 없는 대칭형 세장형 몸체의 경우라도 비대칭 와류는 생성된다. 이러한 비대칭 와류는 불필요한 측력 및 요잉모멘트를 발생시키고 이는 곧 방향 안전성을 저하시킨다. 본 연구는 전산해석을 통하여 초음속유동하에서 세장형 몸체 주변에 발생되는 비대칭와류 모사를 실시하였으며 비대칭 와류의 모사를 위해 선두부에 Bump를 장착하였다. 전산해석 결과 세장형 몸체 주변에 발생하는 비대칭와류를 모사 할 수 있었다.

  • PDF