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Wind and Structures Volume 37, Number 1, July 2023 , pages 57-78 DOI: https://doi.org/10.12989/was.2023.37.1.057 |
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Quasi-steady three-degrees-of-freedom aerodynamic model of inclined/yawed prisms: Formulation and instability for galloping and static divergence |
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Cristoforo Demartino, Zhen Sun, Giulia Matteoni and Christos T. Georgakis
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| Abstract | ||
| In this study, a generalized three-degree-of-freedom (3-DoF) analytical model is formulated to predict linear aerodynamic instabilities of a prism under quasi-steady (QS) conditions. The prism is assumed to possess a generic cross-section exposed to turbulent wind flow. The 3-DoFs encompass two orthogonal horizontal directions and rotation about the prism body axis. Inertial coupling is considered to account for the non-coincidence of the mass center and the rotation center. The aerodynamic force coefficients—drag, lift, and moment—depend on the Reynolds number based on relative flow velocity, angle of attack, and the angle between the wind and the cable. Aerodynamic forces are linearized with respect to the static equilibrium configuration and mean wind velocity. Routh-Hurwitz and Liénard and Chipart criteria are used in the eigenvalue problem, yielding an analytical solution for instabilities in galloping and static divergence types. Additionally, the minimum structural damping and stiffness required to prevent these instabilities are numerically determined. The proposed 3-DoF instability model is subsequently applied to a conductor with ice accretion and a full-scale dry inclined cable. In comparison to existing models, the developed model demonstrates superior prediction accuracy for unstable regions compared with results in wind tunnel tests. | ||
| Key Words | ||
| aerodynamic damping; aerodynamic stiffness; galloping; quasi-steady; static divergence; three degrees-offreedom | ||
| Address | ||
| Cristoforo Demartino:1)Zhejiang University - University of Illinois at Urbana Champaign Institute, Zhejiang University, Haining 314400, Zhejiang, PR China 2)Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA Zhen Sun:Construct-ViBest, Faculty of Engineering (FEUP), Univ. of Porto, Porto, Portugal Giulia Matteoni:Arup, 13 Fitzroy Street, London W1T 4BQ, United Kingdom Christos T. Georgakis:Department of Civil and Architectural Engineering, Aarhus University, Aarhus, Denmark | ||