Aeroacoustic simulations of two co-rotating propellers at low Reynolds number with installation effects

In this study, the sound radiated by two co-rotating propellers mounted side-by-side in close proximity is investigated numerically under low Reynolds number conditions. The pylon-mounted propellers, previously studied experimentally in the literature, are representative of the propellers equipping distributed electric propulsion architectures for aircraft. They consist of six-blade XPROP-S propellers operating at a rotational speed of 7000 rpm with constant pitch angle. Operating conditions at zero advance ratio are considered. The numerical simulations are carried out using a two-step hybrid approach. In the first step, an incompressible large-eddy simulation is performed to compute the flow field. In the second step, tonal and broadband noise predictions with installation effects are obtained using a high-order finite-element approach. The performance of the numerical approach is first verified for a single pylon-mounted propeller. The numerical methodology is then applied to the two-propeller configuration. Acoustic results are successfully compared to experimental data from the literature and further insights into the sound generation mechanisms are provided. In particular, for this zero-advance-ratio propeller configuration, the importance of accounting for propeller–propeller aerodynamic interactions to obtain accurate noise predictions is highlighted. Including installation effects in the acoustic simulations is also found to improve the predictions in the low frequency range.