Abstract
AbstractRecent research developments have indicated that substantial reduction of both the fatigue and ultimate loads can be achieved by adopting trailing edge (TE) flap control strategies. Their aeroelastic tools employ blade element momentum (BEM) aerodynamic models enhanced with a sectional 2D treatment of the TE flap, neglecting the 3D effect of the trailed vorticity in the vicinity of the moving flap. In the present paper, a cross comparison of the BEM‐based models used in the aeroelastic analysis tools against higher fidelity, free‐wake lifting line, and fully resolved CFD models is performed, with the aim to highlight limitations of the first. A second level of comparison assesses the differences among tools of the same level of fidelity from different research groups. Moreover, a number of engineering‐based correction models that are used in conjunction with BEM and account for the complex 3D trailed vorticity effect are assessed. Simulations of a stiff rotor configuration of the DTU 10 MW Reference Wind Turbine are performed for a prescribed, harmonic TE flap motion, and aerodynamic loads are compared at the sectional and rotor‐integrated level. For the studied stiff rotor with the chosen flaps configuration, the results of the code‐to‐code comparisons indicate that low‐fidelity BEM tools consistently predict 1P variations of the rotor thrust due to the TE flap motion, but fail to reproduce the details of the load distributions especially in the vicinity of the flap section. BEM‐based corrected models, which account for 3D‐induced velocity effects, provide load distribution predictions closer to higher fidelity free‐wake and CFD models.
Highlights
The wind community has set a target of increasing the size of the big offshore turbines towards the rating of 20 MW
In order to better assess the aerodynamic influence of the oscillating flap on the loading and on the power performance of the rotor, rotor flexibility is suppressed in the present analysis
A database of reference predictions of aerodynamic loads on rotating blades equipped with trailing edge (TE) flap has been established using a range of tools of different fidelity
Summary
The wind community has set a target of increasing the size of the big offshore turbines towards the rating of 20 MW. In the case of separated flow conditions, the separated flow component of the ONERA model is superimposed to the potential loads provided by the free-wake model.[39] In order to take into account the effect of the moving TE flap in the lifting line model, the CL polars of the sections equipped with flaps should be provided for different flap angles (in particular their slope dCL/dα and the zero lift angle α0). FLOWer was continuously enhanced for wind turbine and helicopter application at the Institute of Aerodynamics and Gas Dynamics, University of Stuttgart,[44] for example, time-accurate FSI or consideration of resolved atmospheric inflow conditions One of these enhancements is a functionality to realize trailing or leading edge flaps based on grid deformation using radial basis functions,[21] which is applied in the present work. A number of 35 nodes are distributed across the blade boundary layer using a geometrical progression of 1.14 growth rate
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