Vortex buffeting of aircraft tail: Interpretation via proper orthogonal decomposition

The proper-orthogonal-decomposition method is applied to particle-image-velocimetry (PIV) data to extract the most energetic flow structures of vortex-tail interaction. The reconstructed flowfields, in conjunction with patterns of vorticity and streamline topology, are compared with the original PIV data on a crossflow plane. The reconstructed flowlields using 5 and 10 eigenfunctions can predict the largest-scale features of the original flowfield. However, the smaller-scale flow structures, which are evident in the original PIV image, are lost. In other words, the flow features of smaller scale can be filtered out by employing the first few eigenmodes. By employing 40 eigenmodes, the reconstructed flowfield can reproduce most of the smaller-scale flow structures of the original flowfield. In terms of the kinetic energy of the fluctuations, about 80% of the total flow energy can be accounted for using 40 eigenmodes.