• Title/Summary/Keyword: 2차원 날개 단면

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Numerical Simulation of Turbulent Flow around 2-D Airfoils in Ground Effect (CFD에 의한 2차원 지면 효과익 주위의 난류유동계산)

  • H.H. Chun;R.H. Chang;M.S. Shin
    • Journal of the Society of Naval Architects of Korea
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    • v.39 no.3
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    • pp.28-40
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    • 2002
  • Turbulent flows around two-dimensional wing sections in ground effect are analysed by incompressible RANS equations and a finite difference method. The Baldwin-Lomax algebraic turbulence model is used to simulate high Reynolds number flows. The main purpose of this study is to clarify the two-dimensional ground effect and its flow characteristics due to different ground boundary conditions, i.e., moving and fixed bottom boundary. As a first step, to validate the present numerical code, the computational result of Clark-Y(t/C 11.7%) is compared with published numerical results and experimental data. Then, NACA4412 section in ground effect is calculated for various ground clearances with two bottom boundary conditions. According to the computational results, the difference in the lift and moment simulated with the two bottom boundary conditions is negligible, but the drag force simulated by the fixed bottom is to some extent smaller than that by the moving bottom. Therefore, it can be concluded that the drag force measured in a wind tunnel with the fixed bottom could be smaller than that with the moving bottom.

A Study on Stress Recovery Analysis of Dimensionally Reducible Composite Beam Structure with High Aspect Ratio using VABS (VABS를 이용한 높은 세장비를 가진 복합재료 보 구조의 차원축소 및 응력복원 해석기법에 대한 연구)

  • Ahn, Sang Ho
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.29 no.5
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    • pp.405-411
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    • 2016
  • This paper presented the theory related to a two dimensional linear cross-sectional analysis, recovery relationship and a one-dimensional nonlinear beam analysis for composite beam with initial twist and high aspect ratio. Using VABS including related theory, preceding research data of the composite wing structure has been modeled and compared. Cross-sectional analysis was performed and 1-D beam was modeled at cutting point including all the details of real geometry and material. The 3-D strain distribution and margin of safety at recovery point was calculated based on the global behavior of the 1-D beam analysis and visualize numerical results.

Flow Analysis around a Wing Section by a Piecewise Linear Panel Method (부분선형 패널법을 이용한 2차원 날개단면 주위 유동 해석)

  • Park, Gi-Duck;Oh, Jin-An;Lee, Jin-Tae
    • Journal of the Society of Naval Architects of Korea
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    • v.52 no.5
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    • pp.380-386
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    • 2015
  • Panel methods are useful tools for analyzing fluid-flow around a wing section. It has the advantage of fast and accurate calculation, compared to other CFD Methods such as RANS solvers. This paper suggests a piecewise linear panel method in order to improve accuracy of existing panel methods by changing the piecewise constant singularity strength to linear singularity strength(for dipole strength). The piecewise linear panel method adopts the linear distribution of singularity strength, while control point is located at the node of each panel. Formulation of the piecewise linear panel method is given, and some calculation results are shown for typical wing sections.

Design of 2-Dimensional WIG Section by a Nonlinear Optimization Method (비선형 최적화 기법을 이용한 2차원 지면효과익의 형상설계)

  • Hee-Jung Kim;Ho-Hwan Chun
    • Journal of the Society of Naval Architects of Korea
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    • v.36 no.3
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    • pp.50-59
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    • 1999
  • This paper is concerned on the generation of an optimal section of wing in ground effect by a SQP method which is one of nonlinear optimization techniques. A potential panel method is used for the flow analysis and the ground effect is taken into account by an image method. The numerical method is first verified by an inverse problem where a shape of wing section is sought for the prescribed pressure distribution. The purpose of the present paper is to generate a wing section which can give a maximum lift subjected to the design constraints including the height stability which is important in the WIG design. The effect of the tail wing is also included.

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Response Characteristics of Aeroelastic Systems Using Robust Controller (강인한 제어기를 이용한 공탄성 시스템의 응답특성)

  • Na, Sungsoo;Jeong, In-Joo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.15 no.4 s.97
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    • pp.437-444
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    • 2005
  • This paper presents a robust aeroelastic control methodology of a two dimensional flapped wing system exposed to an incompressible flow field. A robust controller is designed using a linear matrix inequality (LMI) approach for the multiobjective synthesis. The design objectives are to achieve a mix of $H_{\infty}$ performance and H₂ performance satisfying constraints on the closed loop pole locations in the presence of model uncertainties. Numerical examples are presented to demonstrate the effectiveness of LMI approach in damping out the aeroelastic response of 3-DOF flapped wing system.

Viscous Flow Analysis around a Wind Turbine Blade with End Plate and Rake (풍력터빈 날개의 끝판과 레이크 효과에 대한 점성유동장 해석)

  • Kim, Ju-In;Kim, Wu-Joan
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.14 no.4
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    • pp.273-279
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    • 2011
  • Turbulent flow analysis around a wind turbine blade was performed to evaluate the power performance of offshore wind turbine. Fluent package was utilized to solve the Reynolds-averaged Navier-Stokes equations in non-inertial rotating coordinates. The realizable k-$\varepsilon$ model was used for turbulence closure and the grid system combining structured and unstructured grids was generated. In the first, lift and drag forces of 2-D foil section were calculated and compared with existing experimental data for the validation. Then torque and thrust of the wind turbine blade having NACA 4-series sections were calculated with fixed pitch angle and rpm. Tip speed ratio was varied by changing wind speed. In the next, three kinds of end plate were attached at the tip of blade in order to increase the power of the wind turbine. Among them the end plate attached at the suction side of the blade was found to be most effective. Furthermore, performance analysis with tilt angle and rake was also performed.

Airfoil Aerodynamic Analysis for Supersonic Business Jet Design (Supersonic Business Jet 설계를 위한 날개 단면 공력 해석)

  • Jang, Won-Geun;Jo, Du-Hyeon;Kim, Chan-Hui;Kim, Hae-Sol;Lee, Jung-Hyeon;Kim, Dong-U;Choe, Seong-Im
    • Proceeding of EDISON Challenge
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    • 2012.04a
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    • pp.89-92
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    • 2012
  • 초음속 항공기를 설계하는데 있어서 일반적인 항공기와는 다른 성능이 요구되는데 그것은 바로 초음속에 의한 충격파가 발생시키는 추가적인 항력을 감소시키는 일이다. 날개의 Airfoil 형상을 결정하기 위해서는 공력 특성을 파악해야 하는데, 이를 알아보는 데 있어서 EDISON_CFD를 사용하였다. 충격파의 생성을 지연시키는 Supercritical Airfoil의 여러 형상에 필요한 격자를 생성하여 비점성, 압축성 유동 해석을 수행하였다. 비교에 필요한 다섯 개의 NASA Supercritical Airfoil을 선정하여, 아음속과 초음속으로 나누어 받음각에 따른 양력계수와 항력계수를 도출하고, 이를 토대로 양항비를 추정해 보았다. 추려진 것 중 가장 우수한 공력성능을 보이는 airfoil을 선정하였는데 그 결과 NASA SC-0403 airfoil의 공력 성능이 가장 뛰어나 그것을 선정하기로 하였고, 또한 2차원 공력 해석에서 얻은 양력계수를 면적에 대하여 적분하여 날개에서의 양력과 항력을 추정하였다.

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Numerical Study on the Effects of Corrugation of the Gliding Dragonfly Wing (글라이딩 하는 잠자리 날개 주름의 영향에 대한 수치해석적 연구)

  • Kim, Won-Kap;Byun, Do-Young;Park, Hoon-Cheol
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.36 no.9
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    • pp.835-840
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    • 2008
  • We investigate the aerodynamic performance of the dragonfly wing which has the cross-sectional corrugation by using the static 2-dimensional unsteady simulation. Computational condition is at Re=150, 1400 and 10,000 with the angles of attack from 0 to 40 degrees. As computational results, the increment of the lift coefficient by corrugation is nearly constant over the critical angle of attack. Also, upper side corrugation of the wing have very little influence on increase of the lift coefficient.

Computation of Viscous Flows around a Two-dimensional Oscillating Airfoil ( Part 2. with Dynamic Stall ) (진동하는 2차원 날개 단면 주위에 대한 점성 유동장 계산( Part 2. 동적실속이 발생하는 경우 ))

  • Lee, Pyoung-Kuk;Kim, Hyoung-Tae
    • Journal of the Society of Naval Architects of Korea
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    • v.44 no.1 s.151
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    • pp.16-25
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    • 2007
  • Studies of unsteady-airfoil flows have been motivated mostly by efforts to avoid. or reduce such undesirable effects as flutter, noise and vibrations, dynamic stall. In this paper, we carry out a computational study of viscous flows around a two-dimensional oscillating airfoil to investigate unsteady effects in these important and challenging flows. A fully implicit incompressible RANS solver has been used for calculating unsteady viscous flows around an airfoil. The cell-centered End order finite volume method is utilized to discretize governing equations. in order to ease the flow computation for fluid region changing in time, improve the qualify of solution and simplify the grid generation for an oscillating airfoil flow, the computational method adopts a moving and deforming grid generation technique based on the multi-block grid topology. The numerical method is applied for calculating viscous flows of an oscillating NACA 0012 in uniform flow. The computational results are compared with available experimental data. Computed results are compared with experimental data and flow characteristics of the experiment are reproduced well In the computed results.

Computation of Viscous Flows around a Two-dimensional Oscillating Airfoil ( Part 1. without Dynamic Stall ) (진동하는 2차원 날개 단면 주위에 대한 점성 유동장 계산( Part 1. 동적실속이 없는 경우 ))

  • Lee, Pyoung-Kuk;Kim, Hyoung-Tae
    • Journal of the Society of Naval Architects of Korea
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    • v.44 no.1 s.151
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    • pp.8-15
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    • 2007
  • In this paper, numerical calculations are performed to analyze the unsteady flow of NACA airfoil sections. In order to ease the flow computation for the fluid region changing in time, improve the quality of solution and simplify the grid generation for the oscillating foil flow, the computational method adopts a moving and deforming mesh with the multi-block grid topology. The multi-block, structured-unstructured hybrid grid is generated using the commercial meshing software Gridgen V15. The MDM (Moving & Deforming Mesh) and the UDF (User Define function) function of FLUENT 6 are adopted for computing turbulent flows of the foil in pitching motion. Computed unsteady lift and drag forces are compared with experimental data. in general, the characteristics of unsteady lift and drag of the experiments are reproduced well in the numerical analysis.