Influence of Droplet Morphology on Fluid Dynamics and Impact Erosion of Wind Turbine Blades

Abstract

The impact of droplets, such as rain and sea sprays, on wind turbine blade surfaces can cause severe damage through leading-edge erosion (LEE). Current industrial practice has largely relied on empirical fatigue models to predict damage progression and guide maintenance. However, an important limitation of existing models is the assumption on ideal impact conditions, including perfectly spherical droplet and normal incidence, which rarely occur in reality. This study develops a fluid-structure interaction (FSI) model that couples incompressible multiphase flow simulations with finite element (FE) analysis of blade materials. Using this framework, we investigate the impact dynamics of droplets with arbitrary shapes and orientations. The results reveal a positive correlation between the peak impact pressure, the influential area at the pressure peak, and the peak impact force. In contrast, the time of peak force scales inversely due to momentum conservation. From these findings, we propose a $\textit{universal scaling law}$ that relates all key impact loadings to the simple parameter of the droplet $\textit{projection area}$, which can be determined solely from the initial droplet geometry and orientation. This law provides a predictive framework for impact loading dynamics of non-ideal shapes, offering new insights into the mechanisms of LEE and improving the accuracy of erosion predictions for wind turbine blades.