Numerical study of wind turbine blade airfoil ice accretion

Numerical simulation of ice accretion and effects of the ice on the wind turbine blade airfoil aerodynamic characteristics are studied.Reynolds average Navier-Stokes equations are solved to obtain the flow field around the airfoil with k-ω SST turbulence models being used.Droplet trajectories are acquired using Lagrangian method,based on which the local collection efficiency can be obtained with multi-dispersed droplet distribution being considered.According to conservation of mass and energy,ice accretion rate and ice shape are calculated on the premise that heat flow around the airfoil surface is obtained.At the same time,effects of time on ice accretion are taken into account,and the numerical simulation of ice accretion is accomplished using multi time-step method.Ice shapes on the airfoil and the flow field around iced airfoil in various ambient and meteorological conditions are simulated.Comparison of the aerodynamic characteristics is made between the clean and the iced airfoils,illustrating that glaze ice would deteriorate the wind turbine aerodynamic performance more than rime ice which is formed when the temperature is relatively higher.Ice on the airfoil leads to lower lift and higher drag causing lower lift-drag ratio by the maximum of 61%.Also,the iced airfoil may stall at a lower angle of attack,which results in a degradation of the wind turbine performance.