On the numerical simulation of vortex-induced vibrations of oscillating conductors

Aeolian vibrations for electrical overhead transmission line conductors have been investigated for many decades. Special dampers, e.g., Stockbridge dampers or spacer dampers, are mounted on the conductors to suppress these vibrations, which may otherwise lead to the fatigue failure at the points of high strain values. Simulations are routinely carried out in order to estimate the vibration levels, to determine the need of dampers, and to optimize their locations and the impedances. The energy balance principle (EBP) is well established for estimating the vibration amplitudes, and hence, the strain levels in the transmission line conductors. Besides the parameters of the conductor and of the dampers, the aerodynamic forces acting on the vibrating conductor are the main input data required for the energy balance. For the wind power input, researchers still depend on the experimental data of drag and lift forces of a vibrating cylinder obtained from wind tunnel testing. In case of the bundled conductors, many combinations regarding the number of conductors, spacing of the conductors as well as their orientations are possible, which make wind tunnel tests very expensive and formidable. It may be useful to replace the wind tunnel tests by numerical simulations, as far as possible. However, it is indispensable to validate the numerical results first, for at least some special cases, so that they can be used with confidence in the general case. The present paper is a first step towards obtaining the wind power inputs for different configurations of bundled conductors. In the current work, the flow around a vibrating conductor is simulated with the finite-volume method, by considering it as a circular cylinder. The two-dimensional Navier-Stokes equations are solved first. The drag and the lift forces are then calculated by integrating the pressure and the shear values on the boundary of the cylinder, which ultimately cause the impartation of wind power. The numerically obtained wind power input is then compared with that obtained by different researchers in wind tunnel tests. A very good match between the experimental and the numerical values of wind power input is found.