A low-dimensional model for nonlinear bluff-body aerodynamics: A peeling-an-onion analogy

A low-dimensional model based on the Volterra series is utilized to simulate nonlinear bluff-body aerodynamics. The linear and nonlinear outputs of the aerodynamic system are extracted step by step through a peeling-an-onion analogy. The physical significance of aerodynamic nonlinearities is highlighted during the development of a low-dimensional model. The parameters (kernels) of the low-dimensional model are identified based on impulse functions, which offer a significant computational advantage over the full-order models, e.g., a computational fluid dynamics (CFD)-based scheme. The capability of the proposed low-dimensional model in simulating the nonlinear bluff-body aerodynamic effects is first investigated by three nonlinear examples described by phenomenological models, which represent a gust-induced response, a vortex-induced vibration and a coupling interaction of buffeting and flutter of long-span cable-supported bridges. This is followed by a CFD-based example, representing the motion-induced nonlinear effects on a rectangular bluff body, to further examine and discuss the efficiency and fidelity of the simulation of the low-dimensional model for the nonlinear bluff-body aerodynamics. The Volterra series-based low-dimensional model has shown a remarkable potential for applications to nonlinear bluff-body aerodynamics. The two-dimensional applications discussed in this study could be immediately extended to three-dimensional cases by appropriately accounting for the spanwise correlation of aerodynamic effects.