Numerical modelling of hailstone impact on the leading edge of a wind turbine blade

Abstract

The scale of modern blades means that tip speeds in excess of 100ms -1 are now common in utility scale turbines. Coupling this with a hailstone terminal velocity ranging from 9ms-1 to 40ms-1, the relative impact velocity becomes highly significant. There is little published data on the performance of blade materials under these impact conditions and as such this work aims to understand the impact phenomena more clearly and consequently characterize the impact performance of the constitutive blade materials. To better understand hailstone impact, the LS-DYNA explicit dynamics code was employed to simulate hailstone impact on the blade leading edge. A Smooth Particle Hydrodynamics approach (SPH) was chosen to represent the hailstone geometry. It was found that the forces and stresses created during hail impact are significant and in some cases damaging, therefore posing both short and long term risks to the material integrity. It was also found that coating systems such as the gel coat provide essential - and in extreme conditions, sacrificial - protection to the composite substrate.