• 제목/요약/키워드: Attack Flow

검색결과 615건 처리시간 0.028초

정상상태인 박용 TP620 익형의 경계층 특성 연구 (A study on the boundary layer characteristics of TP620 hydrofoil in the steady state)

  • 서봉록;김시영
    • Journal of Advanced Marine Engineering and Technology
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    • 제10권4호
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    • pp.50-56
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    • 1986
  • This report deals with a study on the boundary layer characteristics of TP620 hydrofoil in the steady state by using two dimensional boundary layer theory. On the basis of complex velocity and laminar and turbulent boundary layer theory, the author attempts to know some tendency by evaluating the performance characteristic values of TP620 hydrofoil working in a uniform flow. In deriving characteristic values, he calculates numerically velocity, momentum thickness, skin friction coefficient, shape factor, and displacement thickness on the TP620 hydrofoil working at each attack angle in a uniform flow. Applying this present numerical calculation using Thwaites' and Head's method, the results of boundary layer on the hydrofoil are shown to be influenced by surface velocity and attack angle.

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Effect of the Gurney Flap on a NACA 23012 Airfoil

  • Yoo, Neung-Soo
    • Journal of Mechanical Science and Technology
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    • 제14권9호
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    • pp.1013-1019
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    • 2000
  • A numerical investigation was performed to determine the effect of the Gurney flap on a NACA 23012 airfoil. A Navier-Stokes code, RAMPANT, was used to calculate the flow field about the airfoil. Fully-turbulent results were obtained using the standard ${\kappa}-{\varepsilon}$ two-equation turbulence model. The numerical solutions showed that the Gurney flap increased both lift and drag. These results suggested that the Gurney flap served to increase the effective camber of the airfoil. The Gurney flap provided a significant increase in the lift-to-drag ratio relatively at low angle of attack and for high lift coefficient. It turned out that 0.6% chord size of flap was the best. The numerical results exhibited detailed flow structures at the trailing edge and provided a possible explanation for the increased aerodynamic performance.

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Feedback flow control using the POD method on the backward facing step wall model

  • Cho, Sung-In;Lee, In;Lee, Seung-Jun;Lee, Choong Yun;Park, Soo Hyung
    • International Journal of Aeronautical and Space Sciences
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    • 제13권4호
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    • pp.428-434
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    • 2012
  • Missiles suffer from flight instability problems at high angles of attack, since vortex flow over a fuselage cause lateral force to the body. To overcome this problem at a high angle of attack, the development of a real time vortex controller is needed. In this paper, Proper Orthogonal Decomposition (POD) and feedback controllers are developed for real time vortex control. The POD method is one of the most well known techniques for modeling low order models that represent the original full-order model. An adaptive control algorithm is used for real time control.

마하수 5에서 회전하는 blunt body의 유동 및 열전달에 관한 수치해석 (Numerical Analysis of Flow- and Heat Transfer of a Spinning Blunt Body at Mach 5)

  • 이명섭;이창호;박승오
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2000년도 춘계 학술대회논문집
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    • pp.172-177
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    • 2000
  • In this numerical work, three dimensional supersonic laminar flow and heat transfer of a blunt body(sphere-cone) at Mach 5 is simulated. The effects of angle of attack and the spin rate on the now and heat transfer are analysed. To solve the three dimensional compressible Wavier-Stokes equation, a finite volume method with the modified LDFSS scheme is employed for spatial discretization, and a point SGS implicit method is used for time integration. It is found that the heat transfer rate increases at the windward side and decreases at the leeward side with the angle of attack. The heat transfer rate at all surfaces slightly increases with the spin rate.

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기저면이 경사진 Ogive실린더의 공력특성에 관한 실험적 연구 (Experimental Study for the Aerodynamic Characteristics of Slanted-Base Ogive Cylinder)

  • 맹주성;양시영;오세진
    • 대한기계학회논문집
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    • 제18권10호
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    • pp.2664-2674
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    • 1994
  • Drag, lift, and pitching moment measurements have been made on a range of slanted-base ogive cylinders, using the KANOMAX wind tunnel and balance system. Test Reynolds numbers(based on model maximum diameter) varied from $0.54{\times}10^{5}{\;}to{\;}1.56{\times}10^{5}$. Crossflow velocity maesurement was conducted by 5-hole pitot tube at $Re_{D}=1.46{\times}10^{5}$. For two base angle $({\theta}=30$ and 45 deg.), aerodynamic forces and moment were measured with increasing angle of attack(0~30 deg.). Two types of wake flow were observed, a quasisymetric turbulent closure or a longitudinal vortex flow. Aerodynamic characteristics differ dramatically between the two wake types. It was found that the drag, lift and pitching moment coefficients increased with increasing angle of attack.

NACA0012 Airfoil의 받음각과 유동형태에 따른 공력특성 분석 (Aerodynamic analysis of flow type and angle of attack around a NACA0012 airfoil)

  • 윤정노;양승덕;조태현;이도형
    • EDISON SW 활용 경진대회 논문집
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    • 제1회(2012년)
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    • pp.53-56
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    • 2012
  • 항공기에 작용하는 공기역학적 힘인 양력과 항력은 항공기 날개 설계에서 성능을 좌우하는 성능지수로 주로 이용된다. 본 연구에서는 NACA0012 airfoil 모델의 공력특성을 EDISON 열유체 시뮬레이션 프로그램(이하 EDISON)을 이용해 분석하고 검증해 보았다. 아음속 유동의 특정 조건에서 받음각과 유동형태에 따른 공력특성 분석을 수행하여 받음각에 따라 변하는 양력계수, 항력계수, 양항비, 실속각과 천음속 유동 조건에 맞추어진 마하수 0.5~1.22 영역에서 변하는 항력계수를 기존 데이터와 비교 검증했다.

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와류발생기의 충돌각과 루버각의 상호작용에 의한 열전달촉진 (Heat Transfer Enhancement by the Combined Effect of Louver Angle and Angle of Attack of Vertex Generator)

  • 박병규;정재동;이준식
    • 설비공학논문집
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    • 제14권6호
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    • pp.477-484
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    • 2002
  • A numerical investigation of the performance of the plate heat exchanger with rectangular winglet is conducted to examine the combined effect of vortex generator and louver fins. Velocity and temperature fields and spanwise averaged Nu and friction factor are presented. Enhancement of heat transfer and flow loss penalty is evident. A Parametric study of three factors (Re, angle of attack and louver angle) with levels of 5 (Re= 300, 500, 700, 900, 1100), 4($\alpha=15^{\circ}, 30^{\circ}, 45^{\circ}, 90^{\circ},$), and 4($\beta=0^{\circ}, 15^{\circ}, 30^{\circ}, 45^{\circ}$), respectively, indicates the performance defined by the ratio of heat transfer enhancement to flow loss penalty shows monotonic behavior for each parameter alone but the interactions between parameters is found to be considerable effect on the performance of heat exchanger and should be considered in design. The effect of stamping is also examined.

NACA 0015 익형에 대한 Gurney 플랩의 영향 (Effect of the Gurney Flap on NACA 0015 Airfoil)

  • 유능수;이장호
    • 산업기술연구
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    • 제20권B호
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    • pp.71-76
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    • 2000
  • A numerical investigation was performed to determine the effect of the Gurney flap on NACA 0015 airfoil. A Navier-Stokes code. FLUENT, was used to calculate the flow field about the airfoil. The fully-turbulent results were obtained using the standard ${\kappa}-{\varepsilon}$ two-equation turbulence model. The numerical solutions showed the Gurney flap increased both lift and drag. These results suggested that the Gurney flap served to increase the effective camber of the airfoil. Gurney flap provided a significant increase in lift-to-drag ratio relatively at low angle of attack and for high lift coefficient. It turned out that 0.75% chord size of flap was best. The numerical results exhibited detailed flow structures at the trailing edge and provided a possible explanation for the increased aerodynamic performance.

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Effects of Angles of Attack and Throttling Conditions on Supersonic Inlet Buzz

  • NamKoung, Hyuck-Joon;Hong, Woo-Ram;Kim, Jung-Min;Yi, Jun-Sok;Kim, Chong-Am
    • International Journal of Aeronautical and Space Sciences
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    • 제13권3호
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    • pp.296-306
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    • 2012
  • A series of numerical simulations are carried out to analyze a supersonic inlet buzz, which is an unsteady pressure oscillation phenomenon around a supersonic inlet. A simple but efficient geometry, experimentally adopted by Nagashima, is chosen for the analysis of unsteady flow physics. Among the two sets of simulations considered in this study, the effects of various throttling conditions are firstly examined. It is seen that the major physical characteristic of the inlet buzz can be obtained by inviscid computations only and the computed flow patterns inside and around the inlet are qualitatively consistent with the experimental observations. The dominant frequency of the inlet buzz increases as throttle area decreases, and the computed frequency is approximately 60Hz or 15% lower than the experimental data, but interestingly, this gap is constant for all the test cases and shock structures are similar. Secondly, inviscid calculations are performed to examine the effect regarding angle of attack. It is found that patterns of pressure oscillation histories and distortion due to asymmetric (or three-dimensional) shock structures are substantially affected by angle of attack. The dominant frequency of the inlet buzz, however, does not change noticeably even in regards to a wide range of angle of attacks.

Galloping characteristics of a 1000-kV UHV iced transmission line in the full range of wind attack angles

  • Lou, Wenjuan;Wu, Huihui;Wen, Zuopeng;Liang, Hongchao
    • Wind and Structures
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    • 제34권2호
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    • pp.173-183
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    • 2022
  • The galloping of iced conductors has long been a severe threat to the safety of overhead transmission lines. Compared with normal transmission lines, the ultra-high-voltage (UHV) transmission lines are more prone to galloping, and the damage caused is more severe. To control the galloping of UHV lines, it is necessary to conduct a comprehensive analysis of galloping characteristics. In this paper, a large-span 1000-kV UHV transmission line in China is taken as a practical example where an 8-bundled conductor with D-shaped icing is adopted. Galerkin method is employed for the time history calculation. For the wind attack angle range of 0°~180°, the galloping amplitudes in vertical, horizontal, and torsional directions are calculated. Furthermore, the vibration frequencies and galloping shapes are analyzed for the most severe conditions. The results show that the wind at 0°~10° attack angles can induce large torsional displacement, and this range of attack angles is also most likely to occur in reality. The galloping with largest amplitudes in all three directions occurs at the attack angle of 170° where the incoming flow is at the non-iced side, due to the strong aerodynamic instability. In addition, with wind speed increasing, galloping modes with higher frequencies appear and make the galloping shape more complex, indicating strong nonlinear behavior. Based on the galloping amplitudes of three directions, the full range of wind attack angles are divided into five galloping regions of different severity levels. The results obtained can promote the understanding of galloping and provide a reference for the anti-galloping design of UHV transmission lines.