• Title/Summary/Keyword: Nonplanar Ground

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Study on the Aerodynamic Characteristics of Wings Flying Over the Nonplanar Ground Surface

  • Han, Cheol-Heui;Lee, Kye-Beom;Cho, Jin-Soo
    • International Journal of Aeronautical and Space Sciences
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    • v.3 no.2
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    • pp.82-87
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    • 2002
  • Aerodynamic analysis of NACA wings moving with a constant speed over guideways are performed using an indirect boundary element method (potential-based panel method). An integral equation is obtained by applying Green's theorem on all surfaces of the fluid domain. The surfaces over the wing and the guideways are discretized as rectangular panel elements. Constant strength singularities are distributed over the panel elements. The viscous shear layer behind the wing is represented by constant strength dipoles. The unknown strengths of potentials are determined by inverting the aerodynamic influence coefficient matrices constructed by using the no penetration conditions on the surfaces and the Kutta condition at the trailing edge of the wing. The aerodynamic characteristics for the wings flying over nonplanar ground surfaces are investigated for several ground heights.

Unsteady Aerodynamic Analysis of an Air-Pressure-Levitated High-Speed Ground Vehicle (공압부양 고속 지상운송채의 비정상 공력해석)

  • Cho, Jeong-Hyun;Cho, Jin-Soo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.36 no.8
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    • pp.728-733
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    • 2008
  • Unsteady aerodynamic analysis of an air-pressure-levitated high-speed ground vehicle moving over the nonplanar ground surface are performed using the boundary-element method. The potential flow solution is included in a time-stepping loop and the wake is captured as part of the solution. When the vehicle moving inside the channel, the lift coefficient and the pitching moment coefficient of the vehicle are increased further because the air trapped by the channel increases the ground effect. In other words, the nonplanar ground surface such as the channel decreases further the longitudinal stability of the vehicle. On the other hand, there is little difference between the ground and the channel in the lateral stability of the vehicle because the lift increment due to the nonplanar ground surface such as the channel takes place on both sides of the wing with the same rate of increase.

Longitudinal Static Stability of Wings Flying Over Nonplanar Ground Surfaces (비평면 지면효과를 받는 날개들의 종방향 정안정성)

  • 김학기;조진수;한철희
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.34 no.7
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    • pp.12-17
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    • 2006
  • Longitudinal static stability and steady aerodynamic characteristics of wings flying over nonplanar ground surfaces (rail and channel) are investigated using the boundary-element method. For a channel with it's fence higher than the wing height, the lift and the nose-down pitching moment increase as the gap between the wingtip and the fence decreases. For a rail with it's width wider than the wing span, the lift and the nose-down pitching moment increase as the rail height decreases. Longitudinal static stability of a single wing flying over nonplanar surfaces is worse than the case of the flat ground. In case of tandem wings, longitudinal static stability of the wings flying over the channel is better than the case of the flat ground. It is believed that the present results can be applied to the conceptual design of high-speed ground transporters.

Unsteady Aerodynamic Analysis of the Wing with Flaperon Flying over Nonplanar Ground Surface (비평면 지면 효과를 받는 플래퍼론이 있는 날개의 비정상 공력해석)

  • Joung, Yong-In;Cho, Jeong-Hyun;Cho, Jin-Soo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.35 no.5
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    • pp.369-374
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    • 2007
  • Unsteady aerodynamic characteristics of the wing with flaperon flying over nonplanar ground surface are investigated using a boundary-element method. The time-stepping method is used to simulate the wake shape according to the motion of the wing and flaperon over the surface or in the channel. The aerodynamic coefficient according to the periodic motion of the flaperon is shown as the shape of loop. The rolling moment coefficient of the wing flying in the channel is same as that of the wing flying over the ground surface. The variation range of pitching moment is wider when the wing flies in the channel than over the ground surface. The present method can provide various aerodynamic derivatives to secure the stability of superhigh speed vehicle flying over nonplanar ground surface using the present method.

Steady Aerodynamic Characteristics of a Wing Flying Over a Nonplanar Ground Surface Part I : Rail

  • Han Cheol-Heui;Kim Hak-Ki;Cho Jin-Soo
    • Journal of Mechanical Science and Technology
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    • v.20 no.7
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    • pp.1043-1050
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    • 2006
  • The aerodynamic interaction between a wing and a rail is investigated using a boundary-element method. The source and doublet singularities are distributed on the wing and its guide-way rail surface. The unknown strengths of the singularities are determined by inverting the aerodynamic influence coefficient matrices. Present method is validated by comparing computed results with the other numerical data. Rail width and rail height affect the aerodynamic characteristics of the wing only if the rail is narrower than the wing span. Although the present results are limited to the inviscid, irrotational flows, it is believed that the present method can be applied to the conceptual design of the high speed ground transporters moving over the rail.

Steady Aerodynamic Characteristics of FAST Flying over Nonplanar Ground Surface (비평면 지면을 비행하는 FAST의 정상상태 공력특성)

  • Cho, Yeon-Woo;Cho, Jeong-Hyun;Cho, Jin-Soo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.35 no.6
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    • pp.483-488
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    • 2007
  • The aerodynamic characteristics of FAST(Future Air Speed Transit) combined the body with tandem wing flying over nonplanar ground surface are investigated by using a boundary element method. To validate the present method, results of the present analysis are compared with the experiment and other numerical results. The arrangement of the tandem wing is determined to secure sufficient aero-levitation force and the stability through the analysis of the aerodynamic characteristics of the FAST. The FAST has the maximum lift characteristics when the tandem wing with lower endplate is located at the front side and the rear side of the body. The stability of the FAST can be secured by using the flaperon of the tandem wing.

Semiempirical MO Calculation of Hetero Atom Three-Membered Ring Compounds(II)${\cdot}$N-Nitroso-azirine and-diaziridine

  • Ki Woon Hwang
    • Bulletin of the Korean Chemical Society
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    • v.12 no.3
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    • pp.328-331
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    • 1991
  • Fully optimized MNDO molecular orbital calculations are performed for N-nitroso-azirine (Ⅰ) and-diaziridine (Ⅱ). The ground state geometries show the nonplanar configuration around the imino nitrogen. The nitroso group rotational energy barriers and the ring inversion energy barriers are also discussed.

Study on the Wake Evolution on the Non-Planar Ground Using a Discrete Vortex Method (이산와류법을 사용한 비평면 지면 와류전개 연구)

  • Han, Cheolheui
    • Journal of Institute of Convergence Technology
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    • v.6 no.2
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    • pp.21-24
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    • 2016
  • Accurate simulation of wakeshapes behind a wing is important for the performance prediction of the aircraft and the wake hazard problem in the airport. In the present study, wakeshapes behind a wing inside tunnels are simulated in regard to the development of wing-in-ground effect vehicles. A discrete vortex method with a nonplanar ground modelling is used for the simulation. It was found that the wingtip vortices move toward outboard directions when the wing is in ground effect. When the wing is placed inside tunnels, the wingtip vortices move along the tunnel wall with counter clockwise direction. As the gap between the wingtip and the tunnel decreases, the wingtip vortices move further along the tunnel wall. Both vortices from bothsides of the wing will murge, which will be studied in future using a viscous computation.

Steady Aerodynamic Characteristics of a Wing Flying Over a Nonplanar Ground Surface Part II : Channel

  • Han Cheol-Heui;Kim Hak-Ki;Cho Jin-Soo
    • Journal of Mechanical Science and Technology
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    • v.20 no.7
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    • pp.1051-1058
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    • 2006
  • The steady aerodynamic characteristics of a wing flying over a channel are investigated using a boundary-element method. The present method is validated by comparing the computed results with the measured data. Compared with a flat ground surface, the channel fence augmented the lift increase and induced drag reduction. When the fence is lower than the wing height, the gap between the wingtip and the fence does not affect the aerodynamic characteristics of the wing much. When the fence is higher than the wing height, the close gap increased the lift. The induced drag is reduced when the wing is placed near the ground or at the same height as the fence. It is believed that present results can be used in the conceptual design of the high-speed ground transporters flying over the channel.

Semiempirical MO Calculation of Hetero Atom Three-Membered Ring Compounds (I) : N-Nitroso-aziridine, -oxaziridine, and -dioxaziridine

  • Hwang, Ki-Woon
    • Bulletin of the Korean Chemical Society
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    • v.11 no.5
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    • pp.422-426
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    • 1990
  • Fully optimized MNDO molecular orbital calculations are described for N-nitroso-aziridine (I), -oxaziridine (II), and -dioxaziridine (III). The ground state geometries show the nonplanar configuration around the imino nitrogen. The nitroso group rotational energy barriers are 3.25, 0.43 and 1.18 kcal/mol for I, II and III, respectively. Also the calculated aziridine ring inversion barriers are 3.98, 15.61 and 27.46 kcal/mol for I, II and III, respectively.