A simulation of operational damage for wind turbine blades

A numerical study of how to simulate airborne particle collisions with a 38-m, 1.5-MW horizontal axis wind turbine blade is presented. Two types of particles were analyzed, namely insects and sand grains. Computations were performed using a two-dimensional inviscid flowfield solver coupled with a particle position predictor code. Three locations along the blade were considered: 35%span and characterized by a DU 97-W-300 airfoil, 65%span with a DU 96-W-212 airfoil, and 75%span using a DU 96-W-180 airfoil. Insect simulations were performed to estimate the residual debris thickness on the blade, while sand simulations were performed to compute the surface erosion rate. Results show that the particle impact locations along the blade sections are a function of local angle of attack, local freestreamvelocity, airfoil shape, particle mass and aerodynamics. Insects and sand grains were found to collide primarily in the vicinity of the blade leading edge. The volume of insect debris per unit span of the blade was maximum at r/R = 0.75. The erosion rate due to sand grains was maximum on the low pressure side of the wind turbine blade. An erosion rate approximately ten times higher was observed at r/R = 0.75 as compared with the inboard section at r/R = 0.35. In the proximity of the leading edge, steep angles of impact occurred, and erosion rate had a minimum, while it reached maximum values moving slightly downstream along the blade section.