Wind turbines in atmospheric flow – FSI simulations with hybrid LES-IDDES turbulence modelling

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 rotor 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, the well established improved delayed detached eddy simulation (IDDES) model is employed. An additional set of simulations relies on a novel hybrid turbulence model, developed within the framework of the present work. It consists on the blending of a large eddy simulation (LES) model for atmospheric flow by Deardorff with 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. A first group accounts for a structural multi body dynamic (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. However, it is expected that future simulations of more complex stratification and longer domains will benefit from the developed hybrid 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.

Exploring inflow wind condition on floating offshore wind turbine aerodynamic characterisation and platform motion prediction using blade resolved CFD simulation

“…Contrary to this, the coarse mesh provides rather poor wake predictions. Moreover, Grinderslev et al [16] compared the onshore wind turbine aerodynamic performance considering the turbine flexibility under turbulent inflows using LES and IDDES models, his study revealed that there is no significant difference between both methods on the prediction of separate flows and blades deflection.…”

“…Figure16 Turbulence intensity at different axial positions at hub height (Z=90 m) in the wake region at t=0.9T…”