On the mechanism of divergent cable movement: Contribution of the bistable flow activity in the critical flow regime

This paper studies the contribution of the bistable flow activity on the installation of incipient conditions to provoke divergent stayed-cable movement. The experiment consists of performing dynamic tests on a long (6.1 m) and genuine inclined and smooth-surfaced cable in a wind tunnel. The cable has an outer diameter of 0.219 m and is equipped with 128 pressure taps distributed on seven (7) rings. The range of the Reynolds numbers is covering the critical flow regime around a circular cylinder. The evolution of mean and instantaneous aerodynamic coefficients is discussed and Proper Orthogonal Modes of the pressure pattern are created. The results indicate that both transitory regimes in the critical flow regime could contribute to install cable instability incipient conditions. Seemingly, only the unsteady states in the critical flow regime appear to participate on imposing large cable displacement. The influence of the circularity defect on disturbing flow fields around the circular cylinder has also been confirmed. Furthermore, the bistable flow activity has been clearly identified to contribute strongly in the installation of large-amplitude wind-induced vibrations.