Optimization of bridge cables with concave fillets

In this paper the aerodynamic performance of new cable surfaces with concave fillet are examined and compared to plain, dimpled and helically filleted surfaces. To this end, an extensive wind-tunnel campaign was undertaken. Preliminary flow visualizations tests and static tests were performed to better understand the structure and development of the wake and the related aerodynamic forces. Subsequent improvements in design were focused on drag reduction and rain rivulet suppression. For this purpose a number of samples with different concave fillet’s height were tested in static condition to estimate the aerodynamic forces. Both new cable surfaces outperform traditional surfaces in terms of rain-rivulet suppression thanks to the ability of the concave shape of the fillet to act as a ramp for the incoming rain-rivulet. Furthermore, both improved innovations with lowest height of the concave fillet show optimal drag coefficients in the supercritical Reynolds range and an early suppression of vortex shedding formation.