Efficient Predictions of Unsteady Viscous Flows Around Bluff Bodies by Aerodynamic Reduced Order Models

Abstract

This paper describes an efficient reduced order model (ROM) applied in the aerodynamic analysis of bluff bodies. The proposed method, which is based on eigensystem realization algorithm (ERA), uses the impulse response of the system obtained by computational fluid dynamics (CED) analysis to construct a ROM that can accurately predict the response of the system to any arbitrary input. In order to study the performance of the proposed technique, three different geometries including elliptical and rectangular sections as well as the deck cross section of Great Belt Bridge (GBB) were considered. The aerodynamic coefficients of the impulse responses of the three sections are used to construct the corresponding ROM for each section. Then, the aerodynamic coefficients from an arbitrary sinusoidal input obtained by CED are compared with the predicted one using the ROM. The results presented illustrate the ability of the proposed technique to predict responses of the systems to arbitrary sinusoidal and other generic inputs, with significant savings in terms of CPU time when compared with most CED codes. The methodology described in this paper has wide application in many offshore engineering problems where flexible structures interact with unsteady fluid flow, and should be useful in preliminary design, in design optimization, and in control algorithm development.

Applications of reduced order models in the aeroelastic analysis of long-span bridges

“…Based on this property, as ∑ D includes very small singular values, UD∑DVDT is negligible compared to UR∑RVRT (Ebrahimnejad et al , 2014b).…”

“…The authors have recently showed the results of ERA-based aerodynamic ROM for a long-span bridge with and without guide vanes (Ebrahimnejad et al , 2012). Also, this procedure has been successfully applied to a bridge section and two simple canonical sections with the same chord length in Ebrahimnejad et al (2014a) and three super long-span bridges in Ebrahimnejad et al (2014b). This work develops the method proposed in Ebrahimnejad et al (2014a, 2012, 2014b) to perform aeroelastic analysis by coupling a pertinent aerodynamic ROM and compatible reduced DOF structural system.…”