Experimental investigation and mechanism analysis of flow-induced vibration by using a cantilever beam-like turbine cascade

Flow-induced vibration (FIV) poses a critical challenge to the performance and structural integrity of turbomachinery blades. Current experimental methodologies for investigating FIV often suffer from inherent limitations: configurations are either oversimplified to the extent of losing representativeness, or excessively complex, hindering effective numerical validation. To bridge this gap, this study introduces an experimentally validated innovative cantilevered turbine cascade. The blade design features a clamped root with a free tip and integrates internal cooling channels to account for thermal gradient effects. Separation-induced vibrations are systematically examined through experiments conducted at three Mach numbers and six incidence angles, with underlying mechanisms elucidated via high-fidelity numerical simulations. The initial phase of the study was performed under room-temperature conditions. Vibration strain near the blade root was monitored concurrently with the surface pressure measurements at 75% span. Experimental pressure distributions show excellent agreement with numerical predictions. Both Mach number and incidence angle primarily affect the unsteady flow characteristics (vortex structure and flow frequency) by altering the onset position of laminar-turbulent transition and the size of the separation bubble. The flow field exhibits broadband frequency content ranging from 1.6 to 230 kHz, whereas the blade's dynamic response is dominated by its first-order bending mode at 177.05 Hz. Experimental results demonstrate that the unsteady flow excites the blade through a broadband energy transfer mechanism rather than via excitation at a single dominant frequency or isolated characteristic scale.