The vortex structure formed by the trailing edge cutback lip induces intense unsteady effects on the cutback surface, thereby significantly influencing the distribution of coolant films, which in turn affects cooling performance. This study experimentally investigates the unsteady film cooling behavior on a trailing edge cutback surface under blowing ratios (BR) ranging from 0.5 to 1.5. Using hot-wire anemometry (HWA) and fast-response pressure-sensitive paint (fast-PSP), the velocity fluctuation spectra and instantaneous cooling effectiveness are analyzed. Spectral analysis identifies increasing vortex shedding frequencies with the rising blowing ratio, while a transition from mainstream-dominated to coolant-dominated flow occurs above BR = 0.7. Time-averaged cooling effectiveness remains excellent (η 0.9) upstream of X/L = 6, but declines thereafter, with higher blowing ratios improving coolant coverage. However, instantaneous film cooling effectiveness distributions reveal significant unsteadiness, characterized by fragmented film patterns. Spectral proper orthogonal decomposition (SPOD) and cross correlation analysis indicate an association between the degradation of cooling performance and the presence of Brown–Roshko (B–R) vortex structures. Furthermore, the dominant frequencies identified via SPOD agree with the HWA results. At lower blowing ratios, coherent mainstream vortices induce strong fluctuations, while higher blowing ratios produce finer coolant vortex structures that enhance film cooling performance. These findings provide essential insights not only into steady-state conditions but more importantly into the unsteady behavior of trailing-edge cutback cooling, thereby informing the optimization of blade cooling design.
Du et al. (Sun,) studied this question.