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Keywords:

  • ice throw;
  • trajectory model;
  • lift effects

ABSTRACT

A model of the trajectories of ice fragments thrown from a rotating wind turbine blade is used to estimate the ground impact locations that could occur under different scenarios. Wind speed, ejection position on the blade and turbine rotation rate all play a role in determining the impact point, as well as mass, density and drag coefficient of the ice fragment. For ‘compact’ ice fragments, the trajectory depends on the combination CDAM where CD is the drag coefficient, A is the frontal area and M the mass of the ice fragment. Sensitivity tests show that ice fragments can travel further laterally for low CD and further downwind for high CD. For plate-like fragments, aerodynamic lift can increase the distance travelled if the plate maintains an orientation to maximize lift. Although this may be a relatively rare event, we provide an example where a 1 kg plate-like fragment could travel up to 350 m from the base of the turbine. Copyright © 2011 John Wiley & Sons, Ltd.