Contra-rotating rotor PIV measurements
Cheng CAO, Zhida MA, Xiangtian LI, Wangqiao CHEN, Peng ZHOU and Xin Zhang
Last updated on April 1, 2026
Contra-rotating rotors in advanced unmanned aerial vehicles (UAVs) can offer enhanced aerodynamic performance and pose significant aeroacoustics challenges. This study experimentally investigates the far-field noise characteristics and flow-field of a 21.8 cm diameter contra-rotating rotors system during axial descent with the effects of varying rotational speeds (60–100 RPS) and descent rates (Vd from 0 m/s to 12 m/s). Experimental results show that the contra-rotating rotor noise increase slightly at low descent rates, decrease sharply at descent ratio Vd/Vh around 1.8 (Vd/Vh is defined as descent speed divided by induced speed while hovering), and rise again when Vd/Vh>2. Directivity results exhibit a dipole characteristic. Tonal noise i
