A spectral model generalising the surface perturbations from leading edge erosion and its application in CFD

Abstract

Blade leading edge erosion (LEE) is a major cost driver in the wind energy sector. LEE is caused by the environmental conditions under which the blades operate. The impact energy of the airborne particles striking the leading edge determines the speed of erosion, thus LEE severity grows towards the blade tip and with a turbine’s tip speed. Currently there is no established method for assessing the aerodynamic impact of LEE, either numerically or experimentally caused by a lack of erosion topological data and its stochastic nature. Whilst previous studies investigated specific realisations of real-world erosion—modelling roughness, gouges, pinholes etc.—we propose a novel, reproducible representation of erosion, based on the superposition of waves with different frequencies and directions of propagation. Using lidar surface scans of a LE exposed to a rain erosion test, we demonstrate the possibility of representing surface perturbations from erosion by a simple spectrum, thereby allowing the mathematical representation of eroded surfaces. Furthermore, we demonstrate how the spectral model simplifies the analysis of LEE-affected aerofoils in CFD. Our study thus encompasses the workflow from rain erosion test → surface scan → spectral perturbation model → numerical erosion generation → 2D CFD → performance loss statistics.