Transversal instability of a single sphere in a swing configuration

Abstract

The existence of transverse instability in spherical beacons fixed to the guard line of high voltage transmission lines under a longitudinal wind has been recently reported. Several kinds of motion appear at a wide range of wind speeds, at low wind speed the vortex induced vibration is suggested as a possible responsible for the swinging motion but not for the autorotation motion. In this paper, dynamic tests over a single sphere in a swing configuration and static tests over a single sphere, that have been carried out in order to find the causes that originate autorotation of the spherical beacons, are reported. The identification of the motion types has been performed in dynamic tests, meanwhile static tests give information about the loads over the sphere. In addition, a possible solution to this behaviour based on the control of the sphere boundary layer through dielectric barrier discharge plasma actuator is proposed.