Abstract:
Based on two-dimensional incompressible, unsteady Reynolds averaged Navier-Stokes (URANS) numerical models, aerodynamic admittances of a thin plate, a box-girder section, and a double-girder section are numerically identified. Two types of oncoming flow are considered in the simulations. One is harmonic fluctuating flow, and the other is broadband turbulent flow. Furthermore, the influences of the amplitude of the harmonic flow on the aerodynamic admittances are investigated. Numerical results indicate that, for the case of thin plate, aerodynamic admittance functions obtained from the harmonic flow are in good agreement with the Sears function. This agreement indicates the reliability of the adopted numerical model. With the oncoming turbulent flow, however, the obtained admittance functions substantially differ from those from harmonic wind fields, and exhibit strong stochastic property. Similar to those of the flat plate, the admittances of the box girder section is close to the Sears function. For the flat plate and box girder sections, their admittances from harmonic flows of different amplitudes are basically in accord with each other, showing the insensitivity to the oncoming wind field. However, the results show that the admittance functions of the double-girder section, which is characterized by severe flow separations, exhibit strong dependence on the approaching wind field. This indicates that, for bluff body sections, aerodynamic admittances could not be taken as a function of the sectional configuration only, but rather, a function jointly determined by the configuration and the wind properties.