Applicability study on three numerical methods for identifying aerodynamic admittances

For the numerical identification method of aerodynamic admittance functions, CFD is used to study the aerodynamic admittance functions of flat plate and box girder sections under harmonic fluctuating flow, broadband turbulent flow and vertical indicial wind flow. Firstly, properties of the wind flows, their propagating, and corresponding computational methodologies are investigated in the spatial domain in the absence of the cross sections. Then, CFD simulations are performed with sections being placed in the domain. Finally, the aerodynamic admittance functions of the two sections are identified in different wind fields. Numerical results indicate that, for the thin plate, aerodynamic admittance functions from all the three fields are in good agreement with the known Sears function, indicating reliability of adopted CFD numerical method. For the box girder section, no substantial difference is found between the broadband turbulent and the harmonic fluctuating methods. However, the method of indicial wind flow, which is based completely on linear superposition principle, can result in significant deviation from the other two methods, indicating inapplicability to bluff body sections. As for computational efficiency, the broadband turbulent method is moderate; the harmonic fluctuating method is of lowest efficiency and can be applied to sections of weak (or no) wind field dependence; the Küssner method, which is of the highest efficiency, is only applicable to sections completely independent on wind fields.