Effect of rotor/rotor interactions on blades unsteady loading

A time-accurate simulation is performed to investigate the unsteady flow field of two counter-rotating rotors under design conditions in the present paper with emphasis on the unsteady effect of the rotor/rotor interactions on rotor blades. The results indicate that with a counter-rotating pattern, the strong unsteadiness of the upstream rotor on its pressure surface is caused by the potential repercussion of the downstream rotor, and the upstream wakes and potential interference are the main causes for the strong unsteadiness of the downstream rotor, especially for its blade leading region. Furthermore, the interaction between the two rotors is testified by the frequency analyzing method. The counter-rotating pattern leads to the doubling of pressure fluctuation frequency on the blade surfaces. Meanwhile, by analyzing the aerodynamic force on the blade surfaces, the effect of potential repercussion on the upstream rotor is found stronger than the influence of the upstream wake and potential interference on the downstream rotor; the relative positions between the two rotors also have some influence on the aerodynamic force of each rotor.