Experiments on the transverse aeroelastic instability of a single sphere in a swing configuration under a longitudinal wind

• Published in: Journal of wind engineering and industrial aerodynamics 2019-10, Vol.193, p.103979, Article 103979
• Main Authors: Gómez-Ortega, Omar, Manzanares-Bercial, Raul, Ogueta-Gutiérrez, Mikel, Lopez-Nuñez, Elena, Franchini, Sebastián, Roibás-Millán, Elena, Sanz-Andres, Angel
• Format: Article
• Language: English
• Subjects: Guard cables with beacons; Longitudinal wind; Swinging sphere; Transverse aeroelastic instability; Whirling autorotation
• ISSN: 0167-6105; 1872-8197
• DOI: 10.1016/j.jweia.2019.103979

Overhead power lines are protected from electrical discharges (that occur during storms) by the so-called “guard cables”, which are placed above the power conductors. In some places, they are provided with beacon spheres. A new instability in these cables, under a longitudinal wind, has recently been reported. The motion of the cable can damage their supports, and causing interference with the power lines, leading to cable breakage, and reducing energy availability supplied by the transmission line. The reported instabilities include oscillation and autorotation motions. In previous papers, the vortex-induced vibration has been suggested as the mechanism that can explain the system oscillations at low speed, and presented the lateral quasi-steady aerodynamic force that can justify both the autorotation motion of a sphere and the oscillations at large speed. In this paper, results of wind tunnel tests concerning a simplified system, a single sphere in a swing configuration, are reported, considering the influence of the main parameters involved: cable span and sag, beacon mass, surface roughness, and reduced wind speed. The limits of the regions corresponding to different motion behaviours (oscillation, autorotation, transitions) are presented in the wind velocity-sag map. Autorotation results have been compared with available theoretical models. •Experimental results concerning the transverse instability are presented.•The limits of the motion pattern regions in the wind velocity-sag map are presented.•The influence of the cable span and sag, body mass, and wind speed are reported.•Autorotation results show good agreement with the available theoretical model.