Abstract
A large-eddy simulation (LES) study of vertical-axis wind turbine wakes under uniform inflow conditions is performed. Emphasis is placed on exploring the effects of subgrid-scale (SGS) modeling on turbine loading as well as on the formation and development of the wind turbine wake. In this regard, the validated LES framework coupled with an actuator-line parametrization is employed. Three different SGS models are considered: the standard Smagorinsky model, the Lagrangian scale-dependent dynamic (LSDD) model, and the anisotropic minimum dissipation (AMD) model. The results show that the SGS model has a negligible effect on the mean aerodynamic loads acting on the blades. However, the structure of the wake, including the mean velocity and turbulence statistics, is significantly affected by the SGS closure. In particular, the standard Smagorisnky model with its theoretical model coefficient (i.e., CS∼0.16) postpones the transition of the wake to turbulence and yields a higher velocity variance in the turbulent region compared to the LSDD and AMD models. This observation is elaborated in more detail by analyzing the resolved-scale turbulent kinetic energy budget inside the wake. It is also shown that, unlike the standard Smagorinsky model, which requires detailed calibrations of the model coefficient, the AMD can yield predictions similar to the LSDD model for the mean and turbulence characteristics of the wake without any tuning.
Highlights
Power harvesting from atmospheric turbulent flows can be achieved through both horizontal-axis and vertical-axis wind turbines
The results obtained from the blade element momentum (BEM) theory are shown for comparison
These figures reveal that the SGS model negligibly affects the mean aerodynamic loads acting on the blades and the predictions of all SGS models lay on top of each other
Summary
Power harvesting from atmospheric turbulent flows can be achieved through both horizontal-axis and vertical-axis wind turbines. Atmosphere 2018, 9, 257 interest for wind energy applications to better understand and quantify how the SGS models affect the aerodynamic loads acting on the blades and the formation and recovery of turbine wakes This effect has been well studied and documented in the LES of HAWT wakes [23,24,25,26,27]. The main reason for considering a uniform inflow condition in this study is that, in the absence of mean wind shear and turbulence in the incoming flow, the SGS model mainly controls the transition of the wake to turbulence [24,27] This case will better assess the capability of different SGS models in capturing the point of transition and breakdown location of the wake.
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