Analysis of the influence of gust on the vibration load of a coaxial rigid rotor

Abstract

Gusts can significantly affect the aerodynamic environment of coaxial rotors and thus influence the load calculation results of coaxial rigid rotors. In this paper, an aeroelastic model of a coaxial rigid rotor is established using moderate-deformation beam theory and a free-wake model, and the calculated results are compared with the rotor load data from the XH-59A full-scale wind-tunnel test to verify the accuracy of the computational model. The influence of two gust forms on rotor vibration loads is further analysed. The results show that the rotor load considering rotor/airframe motion coupling is generally smaller than the flapping bending moment of an isolated rotor, indicating that the rotor/airframe motion coupling effect should be considered in the calculation of coaxial rigid-rotor loads. At the same time, the pulse gust has a more significant effect on rotor loads. The calculation results show that, compared with the ramp gust, a 10 m/s pulse gust increases the flapping load at the 0.3R section by approximately 7%. The effects of gusts from different directions on rotor loads are also different. Under the same 10 m/s pulse-gust condition, their influence can be distinguished more explicitly: the vertical gust produces the largest transient load fluctuation, the longitudinal gust mainly changes the equivalent forward speed and causes acceleration/deceleration-related load variation, and the lateral gust mainly induces rotation-direction-related differences with a relatively smaller overall effect. Therefore, during the flight of coaxial rotorcraft, attention should be paid to the influence of gusts on rotor loads to avoid flight safety problems caused by load exceedance.