Aerodynamic loads on wind turbine nacelles under different inflow turbulence conditions

The aerodynamic loads on wind turbine nacelles for range of inflow turbulence conditions are investigated. To this end, a series of wind tunnel experiments are conducted to investigate pressure field distributions over the surface of scaled models of rectangular and ellipsoidal nacelles. It is found that the mean pressure fields on the roof of the rectangular nacelle are similar for all the inflow turbulence cases for respective yaw angles. However, when yaw angle is around 90°, the mean pressure coefficient becomes more negative close to upstream edge with increasing inflow turbulence. For the ellipsoidal nacelle, the magnitude of the mean pressure coefficient increases with decreasing inflow turbulence in the adverse pressure gradient region, although the minimum peak pressure coefficient remains unaffected by inflow turbulence. The overall effect of wind‐induced load on the nacelle surfaces is evaluated by computing force coefficients from the pressure data. It is observed that the peak force coefficients for both rectangular and ellipsoidal nacelles increase with increasing inflow turbulence. The models for the estimation of peak aerodynamic loads on the nacelle surfaces are proposed as functions of inflow turbulence and mean force coefficients and show satisfactory agreement with measurements. Finally, the loads calculated by the GL guideline are compared against the measurements. It is found that the guideline estimation is conservative for design load case (DLC) 6.1, but it underestimates the load by about 35% for DLC 6.2 when the inflow turbulence intensity is 13.2%.