Smart Twisting Active Rotor (STAR) Wind Tunnel Test and Preliminary Predictions – Blade-Vortex Interaction (BVI) Noise Reduction in Low-Speed Descent Flight Conditions

In October 2025, at the large, low-speed wind tunnel facility of the DNW in the Netherlands, a test was conducted using the Smart Twisting Active Rotor (STAR), which was developed within an international consortium. The primary test objectives were to evaluate the ability of active twist technology to improve performance, reduce vibration, reduce noise over a wide range of flight conditions, including hover, level flight, low speed climb to low-speed descent, high load, and high advance ratio. This paper focuses on evaluation of pre-test simulations performed by all partners for the low-speed flight conditions ranging from climb to descent, specifically looking at blade vortex interaction (BVI) noise. Code-to-code comparisons examine the flight condition that is predicted to produce the maximum BVI noise, as well as trim results compared to measured data for blade pitch control settings, flap and lag hinge angles for a range of flight conditions. Blade loads are compared at a specific radial station as well as over the entire rotor disk. Finally, acoustic results are compared for the baseline case on a plane underneath the rotor and for various active twist harmonics and phase angles. The trim and loading results show that many codes predict similar offsets from the measured data and point to areas of possible improvement in predictions.