Abstract
Nacelle wind speed transfer function (NTF) is usually used for power prediction and operational control of a horizontal axis wind turbine. Nacelle wind speed exhibits high instability as it is influenced by both incoming flow and near wake of a wind turbine rotor. Enhanced understanding of the nacelle wind speed characteristics is critical for improving the accuracy of NTF. This paper presents Reynolds-averaged Navier–Stokes (RANS) simulation results obtained for a multi-megawatt wind turbine under both stable and dynamic incoming flows. The dynamic inlet wind speed varies in the form of simplified sinusoidal and superposed sinusoidal functions. The simulation results are analyzed in time and frequency domains. For a stable inlet flow, the variation of nacelle wind speed is mainly influenced by the blade rotation. The influence of wake flow shows high frequency characteristics. The results with stable inlet flow show that the reduction of the nacelle wind speed with respect to the inlet wind speed is overestimated for low wind speed condition, and underestimated for high wind speed condition. Under time-varing inflow conditions, for the time scale and fluctuation amplitude subject to the International Electrotechnical Commission (IEC) standard, the nacelle wind speed is mainly influenced by the dynamic inflow. The variation of inflow can be recovered by choosing a suitable low pass filter. The work in this paper demonstrates the potential for building accurate NTF based on Computational Fluid Dynamics (CFD) simulations and signal analysis.
Highlights
The use of wind power has been developing rapidly all over the world during the past few decades
In order to address these points, this paper investigates the flow around the nacelle region of a horizontal axis wind turbine (HAWT) using Computational Fluid Dynamic (CFD) simulations with the rotor geometry fully modeled
When the inlet velocities are equal to 5 m/s and 9 m/s, the corresponding nacelle wind speeds are higher than those with stable inlet flow, while with the inlet wind speed of 13 m/s, the former is lower than the latter
Summary
The use of wind power has been developing rapidly all over the world during the past few decades. Hu et al [15,16] investigated the near wake characteristics of wind turbine models in an atmospheric boundary layer using PIV measurements. Zhang et al [17] measured the structure of near wake flow downwind of a model wind turbine in a neutral boundary layer using PIV. In order to address these points, this paper investigates the flow around the nacelle region of a HAWT using CFD simulations with the rotor geometry fully modeled. Both stable inflow and dynamic inflow varying in the form of simplified functions are investigated.
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