Numerical Investigation of Actuator Disc Thickness Effect on Predicting the Performance and Far Wake of the Horizontal Axis Wind Turbine

Abstract

In this paper, the actuator disk (AD) method is used to simulate the wind turbine performance and far-wake behavior. In this work, we incorporate the AD method with an axisymmetric full Navier-Stokes solver. In other words, the calculated AD load is suitably distributed on the disc to impose the aerodynamic forces acting on the blade. One important factor among various different factors, which affect the AD modeling prediction considerably, is the utilized grid thickness. In this work, we first choose the grid thickness recommended by the other researches and study the actual thickness of NREL 5MW wind turbine. Next, many other configurations are considered in our AD thickness modeling including a constant thickness and the actual thickness configurations. The latter one has a linear thickness distribution from 3.54 m at the root to 0.7 m at tip. The wind speed is ranged from 3 to 11 m/s consistent with the practical tests performed on the NREL 5MW wind turbine. We calculate the generated power for all the simulated configurations and their percentages of differences. The results show that the lowest difference is about 4.5% for a constant AD thickness of 0.2 m. Therefore, we conclude that the current AD model predicts results very close to the NREL design data. Additionally, this accurate prediction is similarly observed in the other ranges of wind turbine operational speeds.