Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
Aerodynamic and acoustic characterization of a propeller via a lattice-Boltzmann LES
Submission Author:
Mateus Grassano Lattari , SC , Brazil
Co-Authors:
Mateus Grassano Lattari, Victor H. P. Rosa, Cesar Deschamps
Presenter: Mateus Grassano Lattari
doi://10.26678/ABCM.COBEM2021.COB2021-1934
Abstract
Recent advances in electrical motor technology is enabling their application in propellers of civil aviation, such as in delivery in UAVs, urban transport, eVTOLs and small scale regional electrical aircraft. Most of these new applications are expected to operate in highly populated urban areas, making the resulting noise a critical issue. The propeller is a major source of noise in these aircraft and hence the understanding of its main generation mechanism is critical in the design of quiet aircraft. This paper presents a numerical study of aerodynamic and acoustic aspects of an isolated propeller. A lattice-Boltzmann-based Large Eddy Simulation (LES) method is applied to predict the unsteady fluid flow and noise generation. This solution approach leads to a simpler algorithm and lower computational cost in comparison with other LES-based methods, adopting the lattice-Boltzmann equation to solve the large flow scales and the RNG k-ε turbulence model for the sub-grid modeling. The geometry chosen for the analysis is a two-bladed propeller with a 300 mm diameter and the numerical results are compared with measurements available in the literature. The operating conditions comprise a large range of rotational speeds without considering the effect of the freestream velocity. Predictions for the thrust and torque coefficients are analyzed to characterize the aerodynamics of the propeller. The acoustic far-field is analyzed in two steps for the different positions of the polar microphone array used in the measurements. First, the predictions of narrow band power spectral density (PSD) and overall sound pressure level are compared with the experimental data. Second, the signal is split in its tonal and broadband components, owing to the different nature of the noise sources. The results show that the numerical method can predict the aerodynamic coefficients, the sound pressure level at the first BPF and the OASPL within 15%, 2 dB and 2.4 dB, respectively, of the experimental data. Furthermore, the OASPL for high frequencies shows differences lower than 4 dB in relation to the experimental data for different rotational speeds. In addition to the satisfactory agreement between predictions and measurements, the numerical method used in the present study takes approximately 25% of the computational cost of traditional LES.
Keywords
Propeller Simulation, LBM, powerflow, Aeroacoustics, CFD
