Computational Aeroacoustic Prediction of Propeller Noise Using Grid-Based and Grid-Free CFD Methods

Abstract

Two CFD codes are used to simulate noise data for a tandem cylinder experiment and two scaled NASA SR-2 propeller tests. The first code, STAR CCM+, is a grid-based commercial CFD code while the second code, SmartRotor, is an in-house grid-free CFD code which uses a panel method coupled with a discrete vortex method. Good comparison to experiment is achieved, with STAR CCM+ predicting the vortex shedding of the tandem cylinder case within 3 Hz and 10 dB while also predicting first propeller harmonics within 20 and 11 dB for the first and second propeller simulations, respectively. SmartRotor predicted first propeller harmonics within 6 and 37 dB for the first and second experiments, respectively. A parametic study on the influence of blade count on propeller noise was then performed using both codes to simulating the noise of 7-, 8-, and 10-bladed propellers finding quieter operation with increasing blade count.

Aeroacoustics Analysis of Propeller Blade

“…Also, from Figure 13 velocity distribution is maximum at the tip of the propeller. From Figure 15 acoustics around the propeller is ranges from 80dB to 110dB and from Figure 16 acoustics over the propeller blade is ranging from 100dB to 130dB [5].…”

Aeroacoustics Analysis of Propeller Blades

“…Impulsive noise is caused by blade-vortex interactions or large Mach numbers (which do not usually appear on small drone propellers), while broadband noise is produced by turbulence. Hambrey [3] studied propeller noise numerically, and Hambrey successfully reduced impulsive noise in his study. The most widely used aeroacoustics CFD (computational fluid dynamics) method is FW-H. Ning and Hu [4] and Noda et al [5] show that propeller noise can be reduced by slowing down the rotational speed or increasing wing area.…”