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Aerodynamic Centre

The Experts below are selected from a list of 51 Experts worldwide ranked by ideXlab platform

John H G Macdonald – 1st expert on this subject based on the ideXlab platform

  • An analytical solution for the galloping stability of a 3 degree-of-freedom system based on quasi-steady theory
    Journal of Fluids and Structures, 2016
    Co-Authors: Mingzhe He, John H G Macdonald

    Abstract:

    The Aerodynamic forces on a two-dimensional three-degree-of-freedom (3DOF-heave, sway and torsion) body of arbitrary cross-section are considered, for arbitrary wind direction relative to the principal structural axes. The full 3DOF Aerodynamic damping matrix is derived, based on quasi-steady theory, using the commonly-used concept of an Aerodynamic Centre to represent the effect of the torsional velocity on the Aerodynamic forces. The Aerodynamic coefficients are assumed to be consistent functions of only the relative angle of attack. It is shown that the determinant of the quasi-steady Aerodynamic damping matrix is always zero. The galloping stability of the Aerodynamically coupled system is then addressed by formulating the eigenvalue problem, for which analytical solutions are derived for the case of perfectly tuned structural natural frequencies. The solutions define a non-dimensional effective Aerodynamic damping coefficient, indicating how stable the system is. A trivial solution always exists, with zero effective Aerodynamic damping, corresponding to rotation about the Aerodynamic Centre, and relatively simple exact closed-form solutions are derived for the other one or two solutions, the minimum solution defining the stability of the system. Example results are presented and discussed for square, rectangular (aspect ratio 3) and equilateral triangular sections and a lightly iced cable, and they are compared with results using previous solutions for 2DOF translational and 1DOF pure torsional galloping. For the shapes considered it is found that the stability of the 3DOF system is normally close to that of the 2DOF translational system, with a relatively small influence of the stability of the torsional degree of freedom, although in some instances, especially at the critical angles of attack, it can significantly affect the stability.

Mingzhe He – 2nd expert on this subject based on the ideXlab platform

  • An analytical solution for the galloping stability of a 3 degree-of-freedom system based on quasi-steady theory
    Journal of Fluids and Structures, 2016
    Co-Authors: Mingzhe He, John H G Macdonald

    Abstract:

    The Aerodynamic forces on a two-dimensional three-degree-of-freedom (3DOF-heave, sway and torsion) body of arbitrary cross-section are considered, for arbitrary wind direction relative to the principal structural axes. The full 3DOF Aerodynamic damping matrix is derived, based on quasi-steady theory, using the commonly-used concept of an Aerodynamic Centre to represent the effect of the torsional velocity on the Aerodynamic forces. The Aerodynamic coefficients are assumed to be consistent functions of only the relative angle of attack. It is shown that the determinant of the quasi-steady Aerodynamic damping matrix is always zero. The galloping stability of the Aerodynamically coupled system is then addressed by formulating the eigenvalue problem, for which analytical solutions are derived for the case of perfectly tuned structural natural frequencies. The solutions define a non-dimensional effective Aerodynamic damping coefficient, indicating how stable the system is. A trivial solution always exists, with zero effective Aerodynamic damping, corresponding to rotation about the Aerodynamic Centre, and relatively simple exact closed-form solutions are derived for the other one or two solutions, the minimum solution defining the stability of the system. Example results are presented and discussed for square, rectangular (aspect ratio 3) and equilateral triangular sections and a lightly iced cable, and they are compared with results using previous solutions for 2DOF translational and 1DOF pure torsional galloping. For the shapes considered it is found that the stability of the 3DOF system is normally close to that of the 2DOF translational system, with a relatively small influence of the stability of the torsional degree of freedom, although in some instances, especially at the critical angles of attack, it can significantly affect the stability.

Yoshiaki Kodama – 3rd expert on this subject based on the ideXlab platform

  • FLOW COMPUTATION FOR THREE-DIMENSIONAL WING IN GROUND EFFECT USING MULTI-BLOCK TECHNIQUE
    Journal of the Society of Naval Architects of Japan, 2010
    Co-Authors: Nobuyuki Hirata, Yoshiaki Kodama

    Abstract:

    A WIG (Wing In Ground effect) vehicle is expected to be one of the promising super-high speed craft in the next generation. A WIG is characterized by a high lift to drag ratio and a backward shift of Aerodynamic Centre in close proximity to the ground, hence estimating their features accurately is very important in design and safety evaluation. In the present investigation, flows around a three-dimensional wing with end-plates in ground effect are computed by a Navier-Stokes solver. Because of the geometric complexity of the configuration, a multi-block technique is used. In order to clarify the Aerodynamic interaction between the wing and the ground, two boundary conditions on the ground are considered, that is case 1) velocity is equal to the uniform flow and case 2) no slip condition. They correspond to an actual operating condition and a wind-tunnel condition with a ground plate respectively. The flows with different ground heights are computed by the solver. Results are compared with experimental data and the Aerodynamic characteristics in ground effect are discussed.