Turbine blade durability estimation method based on numerical simulation of progressive rain-induced erosion damage

Rain-induced erosion poses a significant challenge to the durability and performance of wind turbine blades and therefore requires advanced predictive tools for its assessment. This study presents a computationally efficient numerical methodology for simulating the progressive erosion of wind turbine blade surfaces subjected to repeated raindrop impacts. The suggested approach combines Finite Element Analysis (FEA) with a multiphysics erosion modelling framework to capture the material degradation mechanisms, based on equivalent plastic strain accumulation over multiple impacts by predicting the eroded surface evolution through a limited number of numerical simulations. The model forecasts the influence of surface shape variation on subsequent droplet impact stress distributions and consequent damage evolution, in contrast to traditional approaches, which consider droplet impacts only on an initially pristine surface and do not account for the effects of progressive surface erosion. Numerical results are validated against experimental data, showing 7% deviation in the erosion pattern. Neglecting the shape variation induced by the surface damage evolution to estimate rain erosion after 3000 cycles can results in a 70% mass loss underprediction and a 54% damage surface size underestimation compared to experimental results. The effect of erosion damage geometry update frequency was quantified proving a geometry upgrades every 500 cycles to be a balance between computational efficiency and solution accuracy. An erosion area accuracy of 7% was reached in approximately 3h by simulating the overall erosion process (N = 3000) on a 32-processors workstation. The linear equivalent plastic strain accumulation hypothesis was verified, suggesting the use of only three impacts to predict plastic accumulation, at the cost of a conservative 17% overestimation of the equivalent plastic strain. The findings demonstrate the effectiveness of the suggested methodology as computationally efficient water erosion evolution simulation procedure while highlighting the open challenges to address, for a more comprehensive simulation of the phenomenon.