Noise Prediction of a Distributed Propulsion System Using the Actuator Line Method

Within this study, the capability of the actuator line method to simulate the noise of a high-lift distributed propulsion system is investigated. Therefore, the blades of three tractor propellers are approximated as lines with several nodes. Using flowfield data of computational fluid dynamic simulations, the acoustic extrapolation is carried out with the Ffowcs Williams-Hawkings approach. The obtained results are then compared to fully resolved simulations, where it is first ensured that the aerodynamic characteristics agree sufficiently. It was found that the noise characteristic is well predicted by the actuator line method, whereas discrepancies occurred in the prediction of propeller-wing interaction noise. Finally, the parameter space was extended by increasing the angle of attack for the configuration in high-lift and stall conditions. Here, the deviations in the acoustic behavior between the actuator line method and fully resolved simulations increase. Nevertheless, the qualitative characteristic of directivity is also well predicted in these conditions. Beside the main advantage of the actuator line method to perform larger propeller parameter studies without creating a body mesh, computational time can be reduced. It was found that for this configuration, a time saving of 10% could be achieved.