Galloping Stability Criterion for a 3-DOF System Considering Aerodynamic Stiffness and Inertial Coupling

Abstract

Inertial coupling and aerodynamic stiffness play important roles in the prediction of galloping stability but have rarely been considered in previous studies. By considering both factors together, a galloping stability criterion framework for a three-degree-of-freedom (3-DOF) system with various translational and torsional frequency combinations was established based on quasi-steady theory. For a system with discrete frequencies, analytical solutions of eigenvalue real parts were derived using a step-by-step perturbation method. A perturbation method based on repeated eigenvalues was used to solve a system with two close translational frequencies and the corresponding analytical solution. When a system had tuned 3-DOF frequencies, an alternative galloping stability criterion considering the influence of aerodynamic stiffness was proposed to estimate galloping under high wind speed. Wind tunnel test results and numerical simulations of a six-bundle conductor with D-shaped icing were employed to verify the validity of the proposed galloping stability criterion framework. Comparisons of the proposed criterion with other existent galloping theories showed that both aerodynamic stiffness and inertial coupling have significant effects on the initiation of galloping. The contribution of inertial coupling becomes significant under high wind speeds where a higher aerodynamic stiffness emerges. Applying an eccentric mass can improve the galloping stability of a system by producing gravity stiffness and inertial coupling. This finding may provide practical guidance for antigalloping design.