• 제목/요약/키워드: Attack Angle

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Performance Analysis of Stabilizer Fin Applied Coanda System (코안다 시스템이 장착된 안정기용 핀의 성능해석)

  • Seo, Dae-Won;Lee, Se-Jin;Oh, Jungkeun
    • Journal of Ocean Engineering and Technology
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    • v.30 no.1
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    • pp.18-24
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    • 2016
  • Stabilizer fins are installed on each side of a ship to control its roll motion. The most common stabilizer fin is a rolling control system that uses the lift force on the fin surface. If the angle of attack of a stabilizer fin is zero or the speed is zero, it cannot control the roll motion. The Coanda effect is well known to generate lift force in marine field. The performance of stabilizer fin that applies the Coanda effect has been verified by model tests and numerical simulations. It was found that a stabilizer fin that applied the Coanda effect at Cj = 0.085 and a zero angle of attack exactly coincided with that of the original fin at α = 26°. In addition, the power needed to generate the Coanda effect was not high compared to the motor power of the original stabilizer fin.

Autopilot Design for Agile Missile with Aerodynamic Fin and Thrust Vecotring Control

  • Lee, Ho-Chul;Choi, Yong-Seok;Choi, Jae-Weon
    • 제어로봇시스템학회:학술대회논문집
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    • 2003.10a
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    • pp.525-530
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    • 2003
  • This paper is concerned with a control allocation strategy using the dynamic inversion which generates the nominal control input trajectories, and autopilot design using the time-varying control technique which is time-varying version of pole placement of linear time-invariant system for an agile missile with aerodynamic fin and thrust vectoring control. Dynamic inversion can decide the amount of the deflection of each control effector, aerodynamic fin and thrust vectoring control, to extract the maximum performance by combining the action of them. Time-varying control technique for autopilot design enhance the robustness of the tracking performance for a reference command. Nonlinear simulations demonstrates the dynamic inversion provides the effective nominal control input trajectories to achieve the angle of attack command, and time-varying control technique exhibits good robustness for a wide range of angle of attack.

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Aeroelastic Analysis of a Wing with Freeplay Considering Effects of Angle-of-Attack (받음각 효과를 고려한 유격이 있는 날개의 공탄성 해석)

  • Kim Jong-Yun;Yoo Jae-Han;Park Young-Keun;Lee In
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2005.04a
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    • pp.295-300
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    • 2005
  • The freeplay, one of the concentrated structural nonlinearities, is inevitable for control surfaces of a real air vehicle due to normal wear of components and manufacturing mismatches. Also aerodynamic nonlinearities caused by a shock wave occur in transonic region. In practice, these nonlinearities induce the limit cycle oscillation (LCO) and decrease the transonic flutter speed. In this study, the fictitious mass method is used to apply a modal approach to nonlinear structural models due to freeplay. The transonic small-disturbance (TSD) equation is used to calculate unsteady aerodynamic forces in transonic region. Nonlinear aeroelastic time responses are predicted by the coupled time integration method (CTIM). This method was also applied to a 3D all-movable control wing to investigate its nonlinear aeroelastic responses. The angle of attack effect on the LCO characteristics has been found to be closely related with the initial pitching moment.

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Supersonic flow bifurcation in twin intake models

  • Kuzmin, Alexander;Babarykin, Konstantin
    • Advances in aircraft and spacecraft science
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    • v.5 no.4
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    • pp.445-458
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    • 2018
  • Turbulent airflow in channels of rectangular cross section with symmetric centerbodies is studied numerically. Shock wave configurations formed in the channel and in front of the entrance are examined. Solutions of the unsteady Reynolds-averaged Navier-Stokes equations are obtained with finite-volume solvers of second-order accuracy. The solutions demonstrate an expulsion/swallowing of the shocks with variations of the free-stream Mach number or angle of attack. Effects of the centerbody length and thickness on the shock wave stability and flow bifurcation are examined. Bands of the Mach number and angle of attack, in which there exist non-unique flow fields, are identified.

Unsteady Force Characteristics on Foils Undergoing Pitching Motion (피칭 운동익에 작용하는 비정상 유체력)

  • Yang Chang-Jo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.2 s.245
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    • pp.117-125
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    • 2006
  • In the present study the unsteady forces acting on the pitching foils such as a flat plate, NACA0010, NACA0020, NACA65-0910 and BTE have been measured by using a six-axis sensor in a circulating water tunnel at a low Reynolds number region. The unsteady characteristics of the dynamic drag and lift have been compared to the quasi-steady ones which are measured under the stationary condition. The pitching motion is available for keeping the lift higher after the separation occurs. Especially, the characteristics of the dynamic lift are quite different from the quasi-steady one at high pitching frequency regions. As the pitching frequency deceases, the amplitude of the dynamic lift becomes closer to the quasi-steady one. However, the phase remains different between the steady and unsteady conditions even at low pitching frequencies. On the other hand, the dynamic drag is governed strongly by the angle of attack.

A Study on Flow Characteristics of a Wells Turbine for Wave Power Conversion Using Numerical Analysis (수치해석을 이용한 파력발전용 웰즈터빈의 유동특성에 관한 연구)

  • ;;;;T.Setoguchi
    • Journal of Advanced Marine Engineering and Technology
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    • v.25 no.1
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    • pp.182-190
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    • 2001
  • The aerodynamics of the Wells turbine has been studied using 3-d, unstructured mesh flow solver for the Reynolds-averaged Navier-Stokes equations. The basic feature of the Wells turbine is that even though the cyclic airflow produces oscillating axial forces on the airfoil blades, the tangential force on the rotor is always in the same direction. Geometry used to define 3-D numerical grid is based upon that of an experimental test rig. The 3-D Wells turbine model, consisting of approximate 220,000 cells is tested of four axial flow rates. In the calculations the angle of attack has been varied between 10˚ and 30˚ of blades, Representative results from each case are presented graphically andy analysed. It is concluded that this technique holds much promise for future development of Wells turbines.

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

  • 서봉록;김시영
    • Journal of Advanced Marine Engineering and Technology
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    • v.10 no.4
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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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    • v.14 no.9
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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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Investigation on the Hydrodynamic Characteristics of Double Plate Steel Rudder for Small Fishing Boat (소형 어선용 이중강판 방향타의 유체역학적 특성 조사)

  • An, N.H.;Park, H.S.
    • Journal of Power System Engineering
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    • v.16 no.6
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    • pp.24-29
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    • 2012
  • In this study, the numerical simulation has been performed to investigate the hydrodynamic evaluation between double plate steel rudder and newly designed foil type rudder for small fishing boat. The simulations are carried out in 2 speed ranges with 7 variations of flow's angle of attack which is at intervals of about 5 degree respectively. As the well-known commercial code, FLUENT and CATIA are used as the solver. The simulation results show that new designed foil type rudder is better than conventional double plate rudder in terms of Lift and Drag of running boat in the water.

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

  • Lee Myung Sup;Lee Chang Ho;Park Seung O
    • 한국전산유체공학회:학술대회논문집
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    • 2000.05a
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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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