Effect of the upper rivulet on the aerodynamic forces and vibration of stay cables in the critical Reynolds number range

Abstract

During the rain-wind-induced vibration (RWIV) process, a water rivulet forms on the surface of stay cables, and the upper rivulet is considered to be an important factor in RWIV formation. The cables also exhibit galloping in the absence of rain. To reveal the effect of a rivulet on galloping and help explain the mechanism of RWIV, from the viewpoint of the Reynolds number effect, a cylinder with an artificial rivulet at multiple angles was tested in wind tunnel experiments. The results show that the rivulet has a significant effect on the aerodynamic force coefficients, and the increase in the rivulet position decreases the onset Reynolds number of TrBL0-1 transition. A large-angle rivulet limits reattachment on the upper surface of the model, and the vortex appears in TrBL1. Due to reattachment, bistability can be observed in the TrBL0-1 and TrBL1-2 transitions, and the wake vortex is suppressed. During the formation of a separation bubble, the aerodynamic forces change dramatically, which affects the aerodynamic damping of the cables and induces galloping instability in most cases. The condition of reattachment on the upper surface of cables may be an important reason for RWIV occurrences.