Wind turbines in atmospheric flow: fluid–structure interaction simulations with hybrid turbulence modeling

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.

Vibrations of wind turbine blades in standstill: Mapping the influence of the inflow angles

“…Validations of the aeroelastic simulation capabilities of HAWC2 have been also performed, including the study of operational configurations and flutter-like instabilities (Madsen et al, 2018;Volk et al, 2020). Several validation efforts have been published concerning the use of the proposed FSI methodology, including single blade and full rotor configurations (Grinderslev et al, 2020a;2020b). While no experimental data are available for the validation of the FSI coupling framework when applied to large wind turbine rotors in standstill, several comparisons with lower fidelity models have been made in order to assess the appropriateness of the implementation.…”

Wind Turbine Response in Waked Inflow: A Modelling Benchmark Against Full-Scale Measurements

“…For the same reason, aeroelastic effects were disregarded in all turbine models. However, note that fully resolved aeroelastic simulations of the NM80 turbine showed rather small effects of the blade deflections on the thrust, power and wake of the turbine due to the high stiffness of the rotor [30,31].…”

Evaluating the accuracy of the actuator line model against blade element momentum theory in uniform inflow

“…However, even with modern supercomputers, it is very challenging to fully resolve the flow around the blades in LES, and this requires the use of body-fitted meshes; see previous works. [12][13][14] As the use of body-fitted meshes is not yet practical for wind farm simulations, the actuator line model (ALM) is widely used to model wind turbines. The ALM is based on the blade element theory using tabulated aerofoil data with the velocities computed from computational fluid dynamics (CFD).…”

“…LES can capture the three‐dimensional unsteady character of the flow around wind turbines and evaluate the wind turbine performance. However, even with modern supercomputers, it is very challenging to fully resolve the flow around the blades in LES, and this requires the use of body‐fitted meshes; see previous works 12‐14 . As the use of body‐fitted meshes is not yet practical for wind farm simulations, the actuator line model (ALM) is widely used to model wind turbines.…”