Experimental Study of Wind Load acting on Wind Turbine Nacelles

Abstract

The paper investigates wind-induced load on wind turbine nacelles through a series of wind tunnel experiments taking into account inflow turbulence and wind direction. First of all, pressure field data is collected using pressure taps distributed over the top, side and rear surfaces of the scaled nacelle model. It is observed that mean pressure distribution for nonturbulent uniform flow and turbulent shear flow cases were similar at lower yaw angle, but for higher yaw angle, pressure coefficient is smaller (more negative) close to the upstream edge when the inflow is turbulent. However, due to enhanced momentum entrainment, the streamwise extent of such strong negative pressure region is smaller. Force coefficient computed from the pressure data shows that the peak load for turbulent inflow case is significantly higher than for nonturbulent uniform inflow case. The measurement data are also used to propose models for peak factor and coefficient of variation, which can be used to estimate peak loads. The proposed models take into account both inflow turbulence and yaw misalignment, and predicted the peak force coefficients which showed satisfactory agreement with measurement. Finally, it was found that the magnitude of the load calculated by the GL guideline was satisfactory for DLC 6.1, but it was underestimated for DLC 6.2.