• 제목/요약/키워드: flutter mechanism

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Investigation on flutter mechanism of long-span bridges with 2d-3DOF method

  • Yang, Yongxin;Ge, Yaojun;Xiang, Haifan
    • Wind and Structures
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    • 제10권5호
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    • pp.421-435
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    • 2007
  • A two-dimensional flutter analysis method (2d-3DOF method) was developed to simultaneously investigate the relationship between oscillation parameters and aerodynamic derivatives of three degrees of freedom, and to clarify the coupling effects of different degrees of freedom in flutter instability. With this method, the flutter mechanism of two typical bridge deck sections, box girder section and two-isolated-girder section, were numerically investigated, and both differences and common ground in these two typical flutter phenomena are summarized. Then the flutter stabilization effect and its mechanism for long-span bridges with box girders by using central-slotting were studied by experimental investigation of aerodynamic stability and theoretical analysis of stabilizing mechanism. Possible explanation of new findings in the evaluation trend of critical wind speed through central vent width is finally presented.

컴플라이언트 메커니즘을 이용한 플러터 실험 장치 설계 (Flutter Experiment Equipment Design with Compliant Mechanism)

  • 이주호;이준성;성열훈;한재흥
    • 한국소음진동공학회논문집
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    • 제22권4호
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    • pp.393-400
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    • 2012
  • This paper deals with a development of 2-DOF flutter experiment equipment which represents a 2-DOF typical section model. For a conventional 2-DOF flutter experiment equipment, it is hard to observe flutter boundary clearly due to the complexity of the experiment equipment. To refine our flutter experiment equipment system, a compliant mechanism based torsional spring is used. Well-designed extruded aluminum pipe works as a torsional spring. SolidWorks and ANSYS are used for modeling, analysis and design of the torsional spring. With this designed torsional spring, the 2-DOF flutter experiment equipment is developed and wind tunnel tests are performed. Clear flutter boundary which is estimated by classical flutter analysis is observed in the experiments.

컴플라이언트 메커니즘을 이용한 플러터 실험 장치 설계 (Flutter Experiment Equipment Design with Compliant Mechanism)

  • 이주호;이준성;성열훈;한재흥
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2012년도 춘계학술대회 논문집
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    • pp.429-434
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    • 2012
  • This paper deals with a development of 2-DOF flutter experiment equipment which represents a 2-DOF typical section model. For a conventional 2-DOF flutter experiment equipment, it is hard to observe flutter boundary clearly due to the complexity of the experiment equipment. To refine our flutter experiment equipment system, a compliant mechanism based torsional spring is used. Well-designed extruded aluminum pipe works as a torsional spring. SolidWorks and ANSYS are used for modeling, analysis and design of the torsional spring. With this designed torsional spring, the 2-DOF flutter experiment equipment is developed and wind tunnel tests are performed. Clear flutter boundary which is estimated by classical flutter analysis is observed in the experiments.

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4인승 선미익형 경항공기 날개 플러터 해석 (Wing Flutter Analysis for 4-Seat Canard-Type Small Aircraft)

  • 이상욱;신정우;김진원;심재열
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2005년도 춘계학술대회논문집
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    • pp.680-683
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    • 2005
  • The wing component model for flutter analysis consisting of stiffness, mass, and aerodynamic model has been constructed based on the full airframe finite element model for 4-seat canard-type small aircraft. A study on wing flutter characteristics has been investigated based on the wing component model constructed using PK method in MSC/NASTRAN for flutter analysis. In addition, wing flutter mechanism for the aircraft under consideration has been analyzed based on the results of normal mode and flutter analysis.

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주파수 영역에서의 2단 접는 날개 공탄성 해석 (Aeroelastic Analysis in Frequency Domain for Wings with Double-Folding Mechanism)

  • 강명구;김기언
    • 한국군사과학기술학회지
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    • 제9권4호
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    • pp.104-113
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    • 2006
  • To identify aeroelastic characteristics of wings with double-folding mechanism, aeroelastic analyses are performed. There are four wing models which consist of one linear model and three nonlinear models. The nonlinear models have one or two freeplay nonlinearties. The describing function method is used to approximately examine nonlinear effects. The aeroelastic module in MSC/NASTRAN is used to study the aeroelastic characteristics of the considered wing models. The effects of the folding mechanism and amplitude ratio are examined. As the amplitude ratio increases, the flutter speeds approach to those of the wing model with only one nonlinearity. The numerical results show that the flutter speeds of the wings with double-folding mechanism can be lower or higher than those of the wing model with only one folding mechanism depending upon the direction of the second folding mechanism.

Identification of eighteen flutter derivatives of an airfoil and a bridge deck

  • Chowdhury, Arindam Gan;Sarkar, Partha P.
    • Wind and Structures
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    • 제7권3호
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    • pp.187-202
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    • 2004
  • Wind tunnel experiments are often performed for the identification of aeroelastic parameters known as flutter derivatives that are necessary for the prediction of flutter instability for flexible structures. Experimental determination of all the eighteen flutter derivatives for a section model facilitates complete understanding of the physical mechanism of flutter. However, work in the field of identifying all the eighteen flutter derivatives using section models with all three degree-of-freedom (DOF) has been limited. In the current paper, all eighteen flutter derivatives for a streamlined bridge deck and an airfoil section model were identified by using a new system identification technique, namely, Iterative Least Squares (ILS) approach. Flutter derivatives of the current bridge and the Tsurumi bridge are compared. Flutter derivatives related to the lateral DOF have been emphasized. Pseudo-steady theory for predicting some of the flutter derivatives is verified by comparing with experimental data. The three-DOF suspension system and the electromagnetic system for providing the initial conditions for free-vibration of the section model are also discussed.

교량 플러터의 공기역학적 수동제어 (Suppression of bridge flutter by passive aerodynamic control method)

  • 권순덕;정성문;장승필
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2002년도 학술대회지
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    • pp.435-438
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    • 2002
  • In this study, a new passive aerodynamic control method is proposed. Control plate which is oscillated by TMD-like mechanism makes flutter stabilizing airflow. Effectiveness of proposed model is verified by experimental and analytical study. In addition, various parameters of the proposed system are investigated. Applicability to long span bridge is also examined. According to the research results, proposed model is very effective in suppressing flutter, and it also shows remarkable robustness.

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Aerodynamic stabilization of central stabilizers for box girder suspension bridges

  • Ge, Yaojun;Zou, Xiaojie;Yang, Yongxin
    • Wind and Structures
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    • 제12권4호
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    • pp.285-298
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    • 2009
  • For long-span suspension bridges with their intrinsic limit in flutter, some counter measures, for example, central stabilizers, should be adopted to improve aerodynamic stability to meet with the appropriate wind resistance requirements. The present paper introduces aerodynamic stabilization for long-span suspension bridges with box girders by using central stabilizers based on Xihoumen Bridge with the main span of 1650 m. The aerodynamic stabilization study covers experimental investigation of sectional model testing, comprehensive evaluation of three central stabilizers and theoretical analysis of stabilizing mechanism related to flutter derivatives, aerodynamic damping and degree participation.

반디호 수출형 시제기에 대한 플러터 매커니즘 분석 (Flutter Mechanism Analysis for Firefly Export Model)

  • 백승길;이상욱
    • 항공우주기술
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    • 제6권1호
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    • pp.35-44
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    • 2007
  • 본 연구에서는 선미익을 채용한 경항공기인 반디호의 수출형 시제기에 대한 플러터 해석을 수행하였다. 내부 하중 생성용 유한요소모델을 기초로 강성 모델을 작성하였고, 중량 통제를 위한 중량 DB에 근거하여 중량 모델을 작성하였다. 공력모델은 DLM을 이용하였다. 작성된 모델을 이용하여 1차 플러터 해석을 수행하였다. 이를 토대로 주요 진동 모드를 구분해 내고, 지상진동시험을 수행하여 진동 특성을 획득하였다. 획득된 고유진동수를 근거로 유한요소모델의 수정이 이루어졌고 2차 해석이 수행되었다. 해석 결과 주요 플러터 근의 특성을 정리하였다. 가장 중요한 플러터 근은 롤 운동을 갖는 강체 모드와 반대칭 주익 피칭 모드의 연계 모드로 판명되었다.

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Phenomenology of nonlinear aeroelastic responses of highly deformable joined wings

  • Cavallaro, Rauno;Iannelli, Andrea;Demasi, Luciano;Razon, Alan M.
    • Advances in aircraft and spacecraft science
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    • 제2권2호
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    • pp.125-168
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    • 2015
  • Dynamic aeroelastic behavior of structurally nonlinear Joined Wings is presented. Three configurations, two characterized by a different location of the joint and one presenting a direct connection between the two wings (SensorCraft-like layout) are investigated. The snap-divergence is studied from a dynamic perspective in order to assess the real response of the configuration. The investigations also focus on the flutter occurrence (critical state) and postcritical phenomena. Limit Cycle Oscillations (LCOs) are observed, possibly followed by a loss of periodicity of the solution as speed is further increased. In some cases, it is also possible to ascertain the presence of period doubling (flip-) bifurcations. Differences between flutter (Hopf's bifurcation) speed evaluated with linear and nonlinear analyses are discussed in depth in order to understand if a linear (and thus computationally less intense) representation provides an acceptable estimate of the instability properties. Both frequency- and time-domain approaches are compared. Moreover, aerodynamic solvers based on the potential flow are critically examined. In particular, it is assessed in what measure more sophisticated aerodynamic and interface models impact the aeroelastic predictions. When the use of the tools gives different results, a physical interpretation of the leading mechanism generating the mismatch is provided. In particular, for PrandtlPlane-like configurations the aeroelastic response is very sensitive to the wake's shape. As a consequence, it is suggested that a more sophisticate modeling of the wake positively impacts the reliability of aerodynamic and aeroelastic analysis. For SensorCraft-like configurations some LCOs are characterized by a non-synchronous motion of the inner and outer portion of the lower wing: the wing's tip exhibits a small oscillation during the descending or ascending phase, whereas the mid-span station describes a sinusoidal-like trajectory in the time-domain.