Papers by Keyword: Aeroelasticity

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Authors: Li Cheng Fang, Shun Ming Li
Abstract: Aeroelasticity in the form of blade flutter is a major concern for designers in the field of turbomachinery. This paper presents a review of the research and development on blade flutter modeling, including the unsteady aerodynamic model, the structural model and flutter prediction methods. Based on the presentation of these models, the fundamental mechanism and effects of different treatments are discussed. At the end of paper, some deficiencies in the research of flutter and difficulties in modeling fluid-solid coupling effects are pointed out, to which attention should be paid in future.
Authors: Laith K. Abbas, Xiao Ting Rui, Piergiovanni Marzocca
Abstract: This paper deals with supersonic/hypersonic flutter analysis of panels. A 3-D rectangular plate element of variable thickness based on absolute nodal coordinate formulation (ANCF) has been developed for the structural model. A continuum mechanics approach for the definition of the elastic forces within the finite element is considered. Both shear strain and transverse normal strain are taken into account. The aerodynamic force is evaluated by considering the first-order piston theory to linearize the potential flow and is coupled with the structural model to account for pressure loading. A provision is made to take into account the effect of arbitrary flow directions with respect to the panel edges. Aeroelastic equations using ANCF are derived and solved numerically. Values of critical dynamic pressure are obtained by a modal approach, in which the mode shapes are obtained by ANCF. A detailed parametric study is carried out to observe the effects of different flow angle directions and aspect ratios on the flutter boundary.
Authors: Pavel Churin, Olga I. Poddaeva
Abstract: This paper shows the relevance of aerodynamic testing of bridge structures, lists the main documents regulating them, and describes the main features and procedures of these tests.
Authors: Ming Xia Fang
Abstract: Considering nonlinear aerodynamic forces and airfoil structure nonlinearity, aeroelasticity of supersonic airfoil was researched. Using the bifurcation diagram, phase diagram and Poincare map,effect of airfoil aeroelasticity by nonlinear aerodynamic forces and parameters of structural hysteresis was analyzed. Research shows that only consider nonlinear aerodynamic force, systematic motion tends to periodic and quasi- periodic LCO movement, and the vibration amplitude of plunge and pitch movement leap with Ma increasing .When taking into account the nonlinear aerodynamic force and structural nonlinearity, with the change of damping factor, the system will appear subcritical and supercritical flutter, and for the influence of nonlinear structure, movement leap of vibration amplitude does not occur. This means the choice of reasonable structure parameters will help to improve the aeroelastic characteristics of airfoil.
Authors: Zhi Hao Yu, Wei Dong Yang, Jie Wu
Abstract: An aeroelastic model and its simulation method of a rotor system are presented. The aeroelastic mode of a rotor is deduced using the multibody system dynamics. The motion equations of the components of rotor system are independent by using Lagrange’s multiplier method, and the differential and algebraic equations are obtained. Equations of the component including joints are deduced to simplify constraint. The angular constraint equations, expressed by Rodriguez parameters, are modified by introducing a nominal motion to avoid singularities caused by large rotations. A large deformation blade component is incorporated. According to the nonlinear implicit expression and high stiffness ratio of the system equations, an implicit integration algorithm combined with the Broyden method is developed, which exhibits excellent numerical stability and good computational efficiency without calculating the Jacobian matrices and their inverse matrices. To verify the validity of the developed method, the transient analysis and aeroelastic analysis of model rotors are imple-mented. The influence of the stability analysis methods, blade structure models on computation is also studied. It demonstrates that the developed method is useful for improving the computation precision of aeroelastic analysis.
Authors: Li Yun Yi
Abstract: This paper elaborates on the similarity theory applied in the design of the full bridge wind tunnel aeroelastic model for the large-span tied-arch bridge and, taking a Yangtze River Bridge as an example, introduces in details the design method and parameter testing for a full bridge aeroelastic model.
Authors: Jie Wu, Wei Dong Yang, Zhi Hao Yu
Abstract: Based on the finite rotation hypothesis, a rigid-flexible coupling dynamic model is developed. It introduces three rigid degrees of freedom with respect to classical moderate deflection beam theory. With quasi-steady theory and pre-described wake model, aerodynamic forces are tightly coupled with structural motions. Structural forces and moments are computed while equations of motions are solved. Sectional loads by three load caculation methods are examined by the analysis results of BO105 and the flight test data of the SA349/2 helicopter. Force integration method can handle vast ranges of computation cases. The predictions are relatively good except for the numerical integrating errors. Accuracy of reaction force method depends on the accuracy of response solutions and can not predict the loads at points between nodes. For the articulated rotor, force integration method shows better results than curvature method on retreating side.
Authors: Rui Li, Chang Hong Tang
Abstract: Firstly, the origin and mathematical mechanism of freeplay nonlinearity ,cubic nonlinearity, hysteresis nonlinearity was analyzed in this paper , and the importance of nonlinear aeroelasticity on structure was pointed out .On the current system of nonlinear aeroelasticity for the method of flutter analysis was summarized. Meanwhile on the mechanism of geometric nonlinearity and analytic methods have been studied, the future direction of the nonlinear aeroelasticity was concluded .
Authors: L.S. Leao, Maurício Vicente Donadon, A.M.G. de Lima, A.G.C. Filho
Abstract: This paper presents a numerical study on the influence of multimodal shunt circuit parameters in the flutter velocity of a typical section under an unsteady airflow. Flutter on typical sections is a kind of self-excited oscillation which can occur due to the interaction with the airflow. In the flutter point, when the critical dynamic pressure is reached, the vibrations of the typical section become unstable and increase fast and significantly in time. As a result, it can lead the structure to failure. Thus, it becomes important to investigate the possibility of reducing the effects of flutter in order to increase the reliability of composite structures during service. In this work, the aero-electromechanical dynamic model formulation is based on the Hamilton principle. The unsteady aerodynamic forces are calculated based on the linearized thin-airfoil theory, proposed by Theodorsen. The passive element responsible for the energy dissipation is a multimodal resonant shunt circuit in series topology, attached to a piezoelectric patch. An iterative solution algorithm is proposed to solve the resultant nonlinear eigenvalue problem. The optimum shunt tuning is firstly performed using Hagood and Flotow’s propositions; then, it is used an heuristic optimization algorithm, based on Differential Evolution. The preliminary results indicate that the flutter speed can be affected by the passive control, both in its mechanical aspect as electrical.
Authors: Suwin Sleesongsom, Sujin Bureerat
Abstract: An aircraft with morphing or adaptive wings can achieve its flight control through structural flexibility. In order to carry out such aircraft control, the wing structure is actuated by an external force. This leads to a change in aircraft aeroelastic and mechanical characteristics during flight such as lift, control effectiveness, divergence, flutter, buckling, and stress. The objective of this research is to demonstrate the aeroelastic and mechanical behaviors of a wing being actuated by external forces. Static and dynamic aeroelastic models of a wing structure subject to external loads are derived. An un-swept rectangular wing box, using a twisting morphing concept, is used for the demonstration. By applying various values of an actuator moment to the wing, aircraft design parameters e.g. flutter, divergence, lift effectiveness, buckling factor, and stress are computed. The investigation shows that the actuating force has an impact on the aeroelastic and mechanical characteristics. This effect should be taken into account during the design/optimization process of a morphing aircraft structure.
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