Computational Study on the Steady Loading Noise of Drone Propellers: Noise Source Modeling with the Lattice Boltzmann Method

In the present study, a new computational methodology is explored to compute the acoustic field of drone propellers using noise source modeling with the lattice Boltzmann method. A simple mathematical model of steady loading noise for predicting the blade passing frequency (BPF) tone and harmonics at low frequencies (100–1000 Hz) is proposed and tested for various types of drone propellers. The computed result is in a reasonably good agreement with NASA’s measured sound pressure level (SPL) for APC-SF and DJI-CF two-blade single drone propellers rotating at 3600–6000 revolutions per minute. It replicates well the feature of an even number of BPF harmonics for the tested model propellers, showing the decaying slope of -6 for the first two BPF and harmonic peaks in the SPL spectrum. Notably, the proposed steady loading noise model shows all components of RPS harmonics with different magnitudes for different blade sizes and rotor arrangements, such as tricopter and quadcopter. The proposed method can be used for predicting and analyzing tones at low frequencies for various types of open rotor systems, such as multicopters and distributed electric propulsion vehicles.