Abstract
Accurate computation of the performance of a horizontal-axis wind turbine (HAWT) using Blade Element Momentum (BEM) based codes requires good quality aerodynamic characteristics of airfoils. This paper shows a numerical investigation of transitional flow over the DU 91-W2-250 airfoil with chord-based Reynolds number ranging from 3 × 106 to 6 × 106. The primary goal of the present paper is to validate the unsteady Reynolds averaged Navier-Stokes (URANS) approach together with the four-equation transition SST turbulence model with experimental data from a wind tunnel. The main computational fluid dynamics (CFD) code used in this work was ANSYS Fluent. For comparison, two more CFD codes with the Transition SST model were used: FLOWer and STAR-CCM +. The obtained airfoil characteristics were also compared with the results of fully turbulent models published in other works. The XFOIL approach was also used in this work for comparison. The aerodynamic force coefficients obtained with the Transition SST model implemented in different CFD codes do not differ significantly from each other despite the different mesh distributions used. The drag coefficients obtained with fully turbulent models are too high. With the lowest Reynolds numbers analyzed in this work, the error in estimating the location of the transition was significant. This error decreases as the Reynolds number increases. The applicability of the uncalibrated transition SST approach for a two-dimensional thick airfoil is up to the critical angle of attack.
Highlights
During the last two decades many countries all over the world have invested in wind energy technology in view of renewable energy targets and carbon emissions reduction [1,2].Recent trends in the wind energy industry present the development of large wind turbines in offshore wind farms
The results shown in this table confirm the similar compliance of all Computational Fluid Dynamics (CFD) codes with the implemented Transition stress transport (SST) turbulence model
The main fluid for the pressure side of the profile is almost linear over the entire rangeFor of angles of attack dynamics (CFD)
Summary
Recent trends in the wind energy industry present the development of large wind turbines in offshore wind farms. The European Wind Energy Association reported that the latest generation of wind turbines had a rated capacity of up to 7 MW and rotor diameters up to 170 m. Offshore wind turbines development tends towards larger wind farms built in deeper waters and further from the coast. Extending the current water depth limit of 50 m for the fixed substructure concepts will significantly expand the potential of the deeper seas for offshore wind farms [3,4,5,6]. One of the main challenges is the verification of numeric codes, both Computational Fluid Dynamics (CFD) and Blade Element Momentum (BEM) codes, for determining the aerodynamic performance of wind turbines at different flow velocity regimes than before
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