Acoustic comparison of propellers

Abstract

This paper presents results of Computational Fluid Dynamics (CFD)results for flows around propellers and compares their aerodynamic performance as well as their acoustics. After some validation of the employed CFD method, using wind tunnel experiments, a modern propeller design was assessed. Using the same baseline blade, different propellers were put together by adding stagger at the blade hub and small variations of the inter-blade angle. The employed method produced results showing differences in the propeller acoustics regarding the frequency spectrum produced by each design and the level of the acoustic tones. The effect of chancing the hub was to generate frequencies in-between the tones of the baseline design while keeping the overall propeller performance the same. The effect of the employed hub changes was to generate tones in-between the harmonics of the fundamental blade passing frequency that dominated the baseline design. Installed and un-installed blades were compared and the results show that the wing, nacelle and fuselage around the blades, influence the obtained level of noise but not the frequency content. Computations for a climbing case also show the strong effect of the flight conditions on the acoustic results.

Estimation of three-dimensional aerodynamic damping using CFD

“…Previous investigations using HMB3 have provided propeller flow validation in both installed and isolated conditions, by comparison with the experimental results of the JORP propeller (17) and the IMPACTA wind-tunnel tests (18,19) . Good agreement was found in terms of aerodynamics and acoustics (14,13) . HMB3 solves the Navier-Stokes equations in integral form and are discretised using a cell-centered finite volume approach on a multi-block grid.…”

“…For this investigation, the in-house CFD solver HMB3 is used. The core functionality of HMB3 is CFD, however its use has been extended in recent years to include whole engineering applications, including helicopter rotor aeroelasticity (12) and propeller validation (13,14) . In addition to this, the time-marching aeroelastic method of HMB3 has been validated with respect to propeller stall flutter for the Commander propeller blade (15,16) .…”

High-Fidelity Computational Fluid Dynamics Methods for the Simulation of Propeller Stall Flutter

“…Good agreement was found in terms of aerodynamics and acoustics [18,24]. HMB3 solves the Navier-Stokes equations in integral form and are discretised using a cell-centred finite volume approach on a multi-block grid.…”

“…where i, j, k represent the cell index, W and R are the vector of conservative variables and flux residual respectively and V i, j,k is the volume of the cell i, j, k. Greater detail on the numerical techniques employed can be found within the previous investigations conducted using HMB3 [17][18][19][20][24][25][26][27]. Several turbulence models, of both URANS and hybrid LES/URANS families, are available in the HMB3 solver.…”

Numerical aeroacoustic analysis of propeller designs

“…Nevertheless, the trend of the normal force coefficient along the blade is well captured. Validation results for this case are more extensively reported in (59) . The IMPACTA wind tunnel model is a 1 to 4.83 scale model of an installed turboprop powerplant and comprises propeller, nacelle, intake, and part of the wing.…”