Parametric and Comparative Assessment of Navier-Stokes CFD Methodologies for Darrieus Wind Turbine Performance Analysis

Navier-Stokes computational fluid dynamics simulations are expected to provide the basis for a deeper understanding of the real behavior of vertical-axis wind turbines. The prediction of the flow field past Darrieus rotors, a popular turbine of this type, requires a good resolution of both the unsteadiness caused by the periodic variation of the modulus and direction of the relative velocity perceived by the blades, and the interaction between the wakes shed by the blades in the upstream region of the rotor and the downstream blades traveling through such wakes. This paper presents a comparative assessment of the predictive capabilities of two substantially different time-dependent Navier-Stokes Reynolds-averaged-based approaches to the analysis of Darrieus turbines. One is based on a commercial code, and the other on an academic research code. A Darrieus rotor configuration previously analyzed by other researchers was selected for this study, which focused on the turbine flow at a tip-speed ratio of 3.3. Aggregate power coefficient comparisons at other regimes are also provided. Solution sensitivity analyses to spatial and temporal grid refinement, domain size and boundary condition modeling aspects for each of the two approaches are provided in the study. A very good agreement is obtained between the two simulation sets, and a fairly good agreement is found between both simulations and available measured data.