Abstract
Abstract. In order to design future large wind turbines, knowledge is needed about the impact of aero-elasticity on the rotor loads and performance and about the physics of the atmospheric flow surrounding the turbines. The objective of the present work is to study both effects by means of high-fidelity rotor-resolved numerical simulations. In particular, unsteady computational fluid dynamics (CFD) simulations of a 2.3 MW wind turbine are conducted, this rotor being the largest design with relevant experimental data available to the authors. Turbulence is modeled with two different approaches. On one hand, a model using the well-established technique of improved delayed detached eddy simulation (IDDES) is employed. An additional set of simulations relies on a novel hybrid turbulence model, developed within the framework of the present work. It consists of a blend of a large-eddy simulation (LES) model by Deardorff for atmospheric flow and an IDDES model for the separated flow near the rotor geometry. In the same way, the assessment of the influence of the blade flexibility is performed by comparing two different sets of computations. The first group accounts for a structural multi-body dynamics (MBD) model of the blades. The MBD solver was coupled to the CFD solver during run time with a staggered fluid–structure interaction (FSI) scheme. The second set of simulations uses the original rotor geometry, without accounting for any structural deflection. The results of the present work show no significant difference between the IDDES and the hybrid turbulence model. In a similar manner, and due to the fact that the considered rotor was relatively stiff, the loading variation introduced by the blade flexibility was found to be negligible when compared to the influence of inflow turbulence. The simulation method validated here is considered highly relevant for future turbine designs, where the impact of blade elasticity will be significant and the detailed structure of the atmospheric inflow will be important.
Highlights
As future wind turbines will have unprecedentedly long and flexible blades, the necessity of understanding the effects of aero-elasticity on the rotor performance and on its structural integrity increases
This study considers blade resolved fluid–structure interaction (FSI) simulations of the 2.3 MW NM80 wind turbine rotor including blade flexibility using a FSI coupling framework combining the computational fluid dynamics (CFD) code EllipSys3D (Michelsen, 1992, 1994; Sørensen, 1995) and the structural solver from the aeroelastic code HAWC2 (Larsen and Hansen, 2007)
This study investigates the phenomenon of aero-elasticity of wind turbines placed in atmospheric flow conditions, by means of high-fidelity numerical methods
Summary
As future wind turbines will have unprecedentedly long and flexible blades, the necessity of understanding the effects of aero-elasticity on the rotor performance and on its structural integrity increases. Large wind turbines interact with a larger part of the atmospheric boundary layer (ABL), often exceeding the height of the atmospheric surface layer This needs consideration in the design phase, as the rotor blades experience a large variation of flow through each revolution, and flow cases which were not relevant to consider for past designs might occur. This needed knowledge can be obtained through highfidelity methods, such as fluid–structure interaction (FSI) simulations, which model the coupled effects of both flow and structure. A more efficient approach often chosen is the use of actuator lines/discs
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