A Study on the Use of Reduced Order Models for Unsteady Fluid Dynamic Analysis of Flexible Structures

Reduced order models (ROMs) are computationally efficient techniques, which have been widely used for predicting unsteady aerodynamic response of airfoils and wings. However, they have not been applied extensively to perform unsteady fluid dynamic analysis of flexible structures in civil engineering. This paper discusses the application of reduced order computational fluid dynamics (CFD) model based on the eigensystem realization algorithm (ERA) in the aerodynamic analysis of flexible structures with arbitrary shaped cross sections. As an example of a civil structure we examine the GBB long-span bridge for which there are published experimental data. The aerodynamic impulse responses of the GBB Bridge are used to construct the ROM, and then the aerodynamic forces due to arbitrary inputs are evaluated and compared to those of the model coupled with an advanced CFD code. Results demonstrate reasonable prediction power and high computational efficiency of the technique that can serve for preliminary design, optimization and control purposes. The methodology described in this paper has wide application in many offshore engineering problems where flexible structures interact with unsteady fluid mechanical phenomena.