Smart Twisting Active Rotor (STAR) Wind Tunnel Test and Preliminary Predictions - Vibration Reduction in Low-Speed Climb/Descent Flight Conditions

Kurzfassung

One of the primary objectives of the Smart Twisting Active Rotor (STAR) wind tunnel test campaign, conducted in October 2025, was to evaluate vibration reduction through active twist actuation. To characterize the vibration control performance as clearly as possible, a dedicated search for the maximum vibration condition was carried out in low-speed climb/descent flight by varying the flight path angle. A vibration index composed of 4/rev nonrotating hub forces and moments showed that the maximum vibration occurred at the 0 deg flight path angle, that is, the level-flight condition. Active twist actuation was then applied at this condition. The resulting changes in measured quantities, such as the vibration index and the rotor effective lift-to-drag ratio, as functions of the active twist control frequency and phase, are analyzed and compared with preliminary prediction results. As expected, test results confirm that twist actuation is effective in reducing vibration, and both the preliminary prediction and test results show similar trends in vibration index changes according to active twist frequency and phase.