Experiment on aeroelastic stability and load characteristics of long flexible blades under parked condition

Under parked condition, the incoming flow to the blades exhibits significant uncertainty, increasing the risk of aeroelastic instability, which is further amplified as blade size increases and weight decreases. This study employs aeroelastic wind tunnel tests to conduct circumferential inflow measurements, obtaining the instability intervals and load characteristics of long flexible blade. The results indicate that a continuous instability region (353°–2°) exists under the leading edge windward (LEW) condition, characterized by a low wind speed for onset of vibration, highlighting a significant instability risk. Under the trailing edge windward (TEW) condition, two discrete instability regions (160°–167°and 190°–194°) are observed, characterized by a marked nonlinear hysteresis effect and path-dependent dynamic responses. For all instability cases, instability manifests as a single-degree-of-freedom aeroelastic instability dominated by the first-order flapwise mode. The TEW condition exhibits a significant load reduction capability, with a mean reduction of 56.08% and 54.39% in flapwise and edgewise moment at the root, respectively. However, this may lead to an increase in torsional loads. The study reveals that under TEW condition, significant load reduction capability is observed at most inflow angles, with aeroelastic instability occurring only at a limited interval of sensitive inflow angles. These findings can provide useful guidance for load control strategies under parked condition.