Spectral proper orthogonal decomposition analysis of trailing edge cutback film cooling flow

Abstract

Spectral proper orthogonal decomposition (SPOD) is performed to identify the spatiotemporal coherent structures of trailing edge cutback film cooling flows. The analyzed data obtained from delayed-detached eddy simulation are validated against the experimental data first, followed by the extraction of SPOD modes and the reconstruction of flow fields using the SPOD modes. Results show that the flow topology of trailing edge cutback film cooling flows is mainly determined by the blowing ratio. At low blowing ratios, the vortex shedding phenomenon is captured by the first leading SPOD mode. Its mode shape corresponds to the bluff-body wake formation of the lip featured by spanwise coherent structures, which enhance the coolant–hot gas mixing process. At high blowing ratios, the vortex shedding phenomenon is represented by both the first and the second leading SPOD modes. In addition to the lip wake mode, the mode of the bluff-body wake formation of the coolant channel rib arises, whose mode shape is featured by transverse coherent structures. These structures enhance the mixing process between the coolant flows. As the blowing ratio increases, the dominating mode gradually transits from the lip wake mode to the rib wake mode. From the SPOD reconstruction study, the deterministic unsteadiness of vortex shedding is found to contribute to a substantial proportion of unsteady kinetic energy, especially at low blowing ratios. These findings help advance the understanding of trailing edge cutback film cooling flow.