Development of a Computational Fluid Dynamics Methodology to Reproduce the Effects of Macroturbulence on Wind Turbines and Its Application to the Particular Case of a VAWT

Abstract

Based on existing reports and databases, most of the installations in highly turbulent sites in fact fail to reach the expected energy yield, resulting in still or underperforming turbines that also give bad press for the technology. A better understanding of the real performance of wind turbines under highly turbulent conditions is then pivotal to ensure the economic viability of new installations. To this end, the possible use of computational fluid dynamics (CFD) techniques could provide notable benefits, reducing the time-to-market and the cost with respect to experiments. On the other hand, it is intrinsically not easy to reproduce properly intense and large-scale turbulence with the techniques of common use for research and industry (e.g., CFD unsteady Reynolds-averaged Navier–Stokes (URANS)), while the only methods that are granted to do so (e.g., direct numerical simulation (DNS) or large eddy simulation (LES)) are often not computationally affordable. Moving from this background, this study presents the development of a numerical strategy to exploit at their maximum level the capabilities of an unsteady RANS approach in order to reproduce fields of macroturbulence of use for wind energy applications. The study is made of two main parts. In the first part, the numerical methodology is discussed and assessed based on real wind tunnel data. The benefits and drawbacks are presented also in comparison to other existing methods. In the second part, it has been used to simulate the behavior under turbulence of a H Darrieus vertical-axis wind turbine, for which unique wind tunnel data were available. The simulations, even if preliminary, showed good matching with experiments (e.g., confirming the increase of power), showing then the potential of the method.

To What Extent Is Aeroelasticity Impacting Multi-Megawatt Wind Turbine Upscaling? A Critical Assessment

“…Along with the creation of a proper wind profile as inflow conditions, the reproduction of a realistic ABL also requires an unsteady, random macroturbulence inside the flow field. While the mean wind shear conditions were already available within CONVERGE [19], the instantaneous turbulence structure is here generated by TuRBUiND (Turbulence Random Boundary U-velocity Inlet Normal Distribution), a model developed by Balduzzi et al [20], at the inlet boundary of the computational domain to allow reproducing realistic atmospheric turbulence structures also in URANS simulations. The basic idea of the original model is the insertion of macroturbulence in the domain by means of a random distribution of velocity perturbations at the velocity inlet.…”