Numerical Investigation of the Noise Generated and Propagated by Eroded and Coated Leading Edge of the NACA 64-618 Airfoil
* Presenting author
Long term surface erosion of wind turbine blades, especially at the leading edge, impairs aerodynamic performance; therefore, brings down efficiency of the blades mostly in the high-speed rotor tip regions. Blade protection provides significant improvements in annual energy production, reduces costly downtime, and protects the integrity of the blades. However, this protection still influences the aerodynamic behavior, and noise characteristics of the wind turbine blades caused by interaction between the impinging turbulence and blade’s leading edge. This paper presents an extensive numerical aeroacoustic approach by analysing the power spectral density of the different shapes of eroded and coated NACA 64-618 wind turbine airfoil and evaluates noise reduction after the protection procedure. Using computational fluid dynamics (CFD), different quasi 2D numerical grids were implemented and special attention was paid to the refinement of the boundary layers. Dominant noise sources were calculated and used as input to a derived formulation of Curle’s analogy implemented in OpenFOAM. Verifications were conducted for the clean profile using available experimental data. Comparing the sound pressure levels of the clean, coated and eroded profiles in the range of chord-based Reynolds number (1.6e6 ≤Re≤1.5e6), results show that, coating clearly improves aerodynamic and aeroacoustic performance of the eroded airfoil.