Aerodynamic characteristics and POD analysis of the long-span bridge under non-uniform flows

The present study investigates the three-dimensional aerodynamic characteristics under non-uniform inflow through wind tunnel tests in comparison with uniform flow. A 4-m-long test model was employed, with ten cross-sectional pressure-measuring planes. The study examines the spanwise distribution of surface pressure and aerodynamic force coefficients, as well as their frequency characteristics. The relationship between wake frequencies, aerodynamic force frequencies, and trailing-edge surface pressure frequencies was analyzed. Proper Orthogonal Decomposition (POD) was applied to the time-frequency analysis results of the wake field. The absolute values of POD modes represent the extracted wake frequency components. Both POD and time-frequency analysis quantitatively characterize the spatial non-uniformity, spectral complexity, and temporal variability of wake frequencies under non-uniform flow. The results indicate that non-uniform wind velocities have a small impact on the mean pressure coefficients but a significant effect on the fluctuating pressure coefficients and aerodynamic force fluctuation coefficients. Larger wind velocity differences in non-uniform profiles lead to more pronounced spanwise non-uniformity in fluctuating pressure coefficients, mean lift coefficients, and POD modal energy distributions. The spanwise distribution of surface pressure frequencies at the trailing edge, high-frequency regions of aerodynamic forces, and wake frequencies is aligned with the trend of the inflow velocity profile.