Spatiotemporal analysis of tip leakage flow in an axial compressor rotor using three-dimensional dynamic mode decomposition

Tip leakage flow (TLF) has a large effect on the compressor performance and is typically characterized by complex vortex structures, such as the tip leakage vortex (TLV), the secondary TLV (S-TLV), and the backflow vortex (BFV). In this study, the three-dimensional dynamic mode decomposition (DMD) method and a flow field reconstruction technique are employed to analyze the spatiotemporal characteristics of the complex unsteady vortex structures in the tip region of an axial compressor rotor under near-stall conditions using a delayed detached eddy simulation. Based on the spatial structure of the DMD modes and the corresponding unsteady vortex structures in the reconstructed flow field, four TLF dynamic modes are identified according to their amplitudes and decay rates; these modes are subsequently designated the BFV mode, the S-TLV mode, the spiral-type breakdown mode, and the dissipation vortex mode. Furthermore, the results demonstrate that the vortex structures of the TLF interact with each other following a cascade from low-frequency, large-scale structures to high-frequency, small-scale structures. Using the particle tracking techniques applied to the reconstructed flow fields, the dynamic characteristics of the TLF are investigated, and the unsteady vortex structures that contribute to the stall are revealed. The vortex characteristics are analyzed using vortex identification methods, and the results reveal that higher frequencies are predominantly associated with the shear component. The spatiotemporal structural characteristics identified in this study provide valuable insights for data-driven prediction and control of the TLV.