• Title/Summary/Keyword: Transonic small disturbance

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Transonic Flutter Suppression of the 2-D Flap Wing with External Store using CFD-based Aeroservoelasticity

  • Lee, Seung-Jun;Lee, In;Han, Jae-Hung
    • International Journal of Aeronautical and Space Sciences
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    • v.7 no.2
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    • pp.121-127
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    • 2006
  • An analysis procedure for the combined problem of control algorithm and aeroelastic system which is based on the computational fluid dynamics(CFD) technique has been developed. The aerodynamic forces in the transonic region are calculated from the transonic small disturbance(TSD) theory. An linear quadratic regulator(LQR) controller is designed to suppress the transonic flutter. The optimal control gain is estimated by solving the discrete-time Riccati equation. The system identification technique rebuilds the CFD-based aeroelstic system in order to form an adequate system matrix which involved in the discrete-time Riccati equation. Finally the controller, that is constructed on the basis of system identification technique, is used to suppress the flutter phenomenon of the airfoil with attached store. This approach, that is, the CFD-based aeroservoelasticity design, can be utilized for the development of effective flutter controller design in the transonic region.

Transonic Aeroelastic Analysis of a Airfoil with Friction Damping (마찰 감쇠를 고려한 에어포일의 천음속 공탄석 해석)

  • Yoo, Jae-Han;Lee, In
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.38 no.11
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    • pp.1075-1080
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    • 2010
  • For the aeroelastic analysis of a wing with friction damping, coupled time integration method was used to obtain time responses in the subsonic and transonic regions. To take into account aerodynamic nonlinearity induced by shock wave on the lifting surface, transonic small disturbance equation with in-phase periodic boundary condition was used for unsteady aerodynamic calculation. For 2-DOF airfoil system with displace-dependent friction dampers, the effects of normal load slope and Mach number on flutter boundary were investigated.

Planform Curvature Effects on the Stability of Coupled Flow/Structure Vibration (면내 곡률이 천음속 및 초음속 유체/구조 연계 진동 안정성에 미치는 영향)

  • Kim, Jong-Yun;Kim, Dong-Hyun;Lee, In
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.12 no.11
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    • pp.864-872
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    • 2002
  • In this study, the effect of planform curvature on the stability of coupled flow/structure vibration is examined in transonic and supersonic flow regions. The aeroelastic analysis for the frequency and time domain is performed to obtain the flutter solution. The doublet lattice method(DLM) in subsonic flow is used to calculate unsteady aerodynamics in the frequency domain. For all speed range, the time domain nonlinear unsteady transonic small disturbance code has been incorporated into the coupled-time integration aeroelastic analysis (CTIA). Two curved wings with experimental data have been considered in this paper MSC/NASTRAN is used for natural free vibration analyses of wing models. Predicted flutter dynamic pressures and frequencies are compared with experimental data in subsonic and transonic flow regions.

A Study of Transonic Combustion in a Diverging Channel Using Asymptotic Analysis (점근해석을 이용한 확대형 채널 내의 천음속 연소에 관한 연구)

  • Lee, Jang-Chang
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.1604-1610
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    • 2004
  • A steady dilute premixed combustion at transonic speeds in a diverging channel is investigated. The model explores the nonlinear interactions between the near-sonic speed of the flow, the small changes in geometry from a straight channel, and the small heat release due to the one-step first-order Arrhenius chemical reaction. The reactive flow can be described by a nonhomogeneous transonic small-disturbance (TSD) equation coupled with an ordinary differencial equation for the calculation of the reactant mass fraction in the combustible gas. The asymptotic analysis results in the similarity parameters that govern the reacting flow problem. The model is used to study transonic combustion at various amounts of incoming, reactant mass, reaction rates, and channel geometries.

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Nonlinear Transonic Flutter Analysis of a Composite Fin Considering Delamination Effect (층간분리 효과를 고려한 복합재 핀의 비선형 천음속 플러터 해석)

  • Gwang Young Lee;Ki-Ha Kim;Dong-Hyun Kim
    • Journal of Aerospace System Engineering
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    • v.17 no.6
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    • pp.82-93
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    • 2023
  • In this paper, nonlinear transonic flutter analyses of a composite missile fin considering the effect of delamination are conducted. An effective modal analysis methodology is adopted and verified with the experimental modal test data for laminated composite plates with delamination. Extended version of the in-house computational aeroelastic analysis program with the transonic small-disturbance (TSD) code is used in order to predict the flutter dynamic pressure of the delaminated composite fin models. In the subsonic, transonic, and supersonic flow regions, nonlinear time-domain flutter analyses are performed for various delamination conditions, and aeroelastic characteristics due to the delamination phenomena are examined in detail.

Transonic Aeroelastic Analyses of Wings Considering UViscous and Thickness Effects

  • Kim, Jong-Yun;Kim, Kyung-Seok;Lee, In
    • International Journal of Aeronautical and Space Sciences
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    • v.9 no.2
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    • pp.34-40
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    • 2008
  • The aeroelastic analyses for several wing models were performed using the transonic small-disturbance (TSD) equation, which is very efficient, to consider the aerodynamic nonlinearities in the transonic region. For more accurate aerodynamic analysis of airfoil and wing models with shock waves, the viscous equations based on the Green's lag-entrainment equation of boundary-layer effects were coupled with the TSD equation in the transonic region. Finally the aeroelastic characteristics of wing models were investigated through comparisons of the aeroelastic analysis results for wing models considering the change of a thickness of the airfoil section. Moreover, the results of the aeroelastic analysis using the coupled TSD equation with the viscous equations were compared with those using the TSD equation for several wing models.

A Study of Transonic Premixed Combustion in a Diverging Channel Using Asymptotic Analysis (점근해석을 이용한 확대형 채널 내의 천음속 예혼합 연소에 관한 연구)

  • Lee, Jang-Chang
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.33 no.8
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    • pp.75-83
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    • 2005
  • A steady transonic dilute premixed combustion in a diverging channel is investigated by using asymptotic analysis. This model explores the nonlinear interactions between the near-sonic speed of the flow, the small changes in geometry from a straight channel, and the small heat release due to the one-step first-order Arrhenius chemical reaction. The reactive flow is described by a nonhomogeneous transonic small-disturbance (TSD) equation coupled with an ordinary differential equation for the calculation of the reactant mass fraction in the combustible gas. Also the asymptotic analysis reveals the similarity parameters that govern the reacting flow problem. The results show the complicated nonlinear interaction between the convection, reaction, and geometry effects and its effect on the flow behavior.

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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Flutter characteristics of a Composite Wing with Various Ply Angles (복합재료날개의 적층각에 대한 플러터 특성 연구)

  • Yoo, Jae-Han;Kim, Dong-Hyun;Lee, In
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2000.04a
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    • pp.126-130
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    • 2000
  • In this study, flutter characteristics of a composite wing have been studied for the variation of laminate angles in the subsonic, transonic and supersonic flow regime. The laminate angles are selected by the aspect of engineering practice such as 0, $\pm$45 and 90 degrees. To calculate the unsteady aerodynamics for flutter analysis, the Doublet Lattice Method(DLM) in subsonic flow and the Doublet Point Method(DPM) in supersonic flow are applied in the frequency domain. In transonic flow, transonic small disturbance(TSD) code is used to calculate the nonlinear unsteady aerodynamics in the time domain. Aeroelastic governing equation has been solved by v-g method in the frequency domain and also by Coupled Time-Integration Method(CTIM) in the time domain. from the results of present study, characteristics of free vibration responses and aeroelastic instabilities of a composite wing are presented for the set of various lamination angles in the all flow range.

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Transonic/Supersonic Flutter Analysis of a Fighter Wing with Tip-Store (끝단 장착물이 있는 항공기 날개의 천음속/초음속 플러터 해석)

  • Kim, Dong-Hyun;Lee, In
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.1198-1203
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    • 2000
  • In this study, a nonlinear aeroelastic analysis system for the fighter wing with tip-store has been developed additionally in the transonic and supersonic flow region. The unsteady CFD code based on the transonic small disturbance theory has been incorporated to consider the numerical capability for the aerodynamic nonlinear effects. The coupled time-integration method is used to observe the detailed nonlinear aeroelastic responses for elastic wings in their flight. condition. A conservative wing-box model of a fighter wing with tip-store is modeled by MSC/PATRAN and the corresponding free vibration analysis has been performed by MSC/NASTRAN. The results of flutter analyses are presented in the subsonic, transonic and supersonic flow regime.

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