Isolation, decomposition, and mechanisms of the aerodynamic nonlinearity and flow field phenomenology of structure-motion-induced dynamics in fluid–structure interactions

Abstract

This study focuses on the aerodynamic nonlinearity and flow field phenomenology of structure-motion-induced dynamics in fluid–structure interactions (FSI), which is essential for response prediction. Through dynamic-meshing large-eddy simulations with near-wall resolution, the nonlinear aerodynamic damping in the still wind has been isolated by forced vibration, and its phenomenological characteristics and physical mechanisms have been analyzed. The results show that nonlinear aerodynamic damping can account for up to 30% of the total damping, which cannot be ignored in response prediction. The study also reveals that the three-dimensional vorticity dynamics vary nonlinearly with structure motion, leading to the hysteresis effect between aerodynamic forces and displacement. Furthermore, in-depth phenomenological analysis discloses eight types of coherent flow field substructures, including the Stick, Phone, Bowknot, Crutch, Droplet, Bat, Horn, and Flag substructures, which are solely induced by structural motion. Insights into these substructures' formation, evolvement, dissipation, and superposable magnitude have been disclosed. This research offers a new perspective on understanding the physical nature of aerodynamic damping in FSI, serving as a reference for various FSI applications, including bridges, high-building design, and other related fields.