Blade Load Unsteadiness and Turbulence Statistics in an Actuator Line Computed Turbine–Turbine Interaction Problem

Abstract

The objective of this study is to investigate how different volumetric projection techniques used in actuatorline modeling affect the unsteady blade loads and wake turbulence statistics. The two techniques for the bodyforce projection radius are based on either (i) the grid spacing or (ii) the combination of grid spacing and an equivalent elliptic blade planform. An array of two National Renewable Energy Laboratory 5MW turbines separated by seven rotor diameters is simulated for 2000 s (about rotor 300 revolutions) within a largeeddy simulation (LES) solver of the neutral and moderately convective atmospheric boundary layer (ABL). The statistics of sectional angle of attack (AOA), blade loads, and turbine power histories are quantified. Moreover, the degree of unsteadiness of sectional blade loads in response to atmospheric and wake turbulence is computed via a reduced frequency based on the rateofchange in sectional AOA. The goal of this work is to make the wind energy community aware of the uncertainties associated with actuatorline modeling approaches.