Effects of turbulent inflow parameters on aerodynamic admittance of a road vehicle on a streamlined bridge girder

Aerodynamic admittance is an important transfer function between turbulent inflow and vehicle buffeting forces. Its accurate determination is important for calculating unsteady aerodynamic forces on vehicles and evaluating driving comfort. For road vehicles on bridge decks, this transfer process is affected by the interaction between incoming turbulence, vehicle geometry, and the local flow field modified by the bridge girder. However, the dependence of vehicle aerodynamic admittance on turbulence intensity and integral length scale remains insufficiently quantified, particularly for road vehicles exposed to bridge deck flow environments. To study the effects of turbulence parameters on vehicle aerodynamic admittance, several representative turbulent wind fields were generated in a wind tunnel using different grids. Wind tunnel tests of a scaled coach model were then carried out. Based on the measured wind speed histories and unsteady aerodynamic force histories, the aerodynamic admittance functions of side force, lift, rolling moment, and pitching moment were identified. The results show that both turbulence integral scale and turbulence intensity affect vehicle aerodynamic admittance. In general, aerodynamic admittance increases with increasing turbulence integral scale. The effect of turbulence intensity is relatively more complex. A function model of aerodynamic admittance was established by considering the turbulence integral scale, turbulence intensity, and vehicle characteristic dimensions. The fitted results agree well with the experimental data. This indicates that the proposed model can reasonably describe vehicle aerodynamic admittance under different turbulent flow conditions and can provide a reference for predicting vehicle buffeting forces.