Jinge Chen

The unsteady aerodynamics of floating wind turbine under platform pitch motion

The aerodynamic performance of floating platform wind turbines is much more complex than fixed-base wind turbines because of the flexibility of the floating platform. Due to the extra six degrees-of-freedom of the floating platform, the inflow of the wind turbine rotors is highly influenced by the motions of the floating platform. It is therefore of interest to study the unsteady aerodynamics of the wind turbine rotors involved with the interaction of the floating platform induced motions. In the present work, a lifting surface method with a free wake model is developed for analysis of the unsteady aerodynamics of wind turbines. The aerodynamic performance of the NREL 5 MW floating wind turbine under the prescribed floating platform pitch motion is studied. The unsteady aerodynamic loads, the transient of wind turbine states, and the instability of the wind turbine wakes are discussed in detail.

Influence of wake asymmetry on wind turbine blade aerodynamic and aeroelastic performance in shear/yawed wind

Wind turbines operate in atmospheric shear layer and often in yawed flow condition, which, among others, produce cyclic fluctuating loads on the blades. The unsteady aerodynamics of wind turbine in both shear and yawed wind are studied in the present work. The rotor aeroelastic behaviors considering blade flexibility are also discussed. An advanced aeroelastic model based on free wake lifting surface model and geometrically exact beam theory is established to conduct the study. The aerodynamic simulations show that the wake is asymmetric in both shear and yawed conditions. Comparison is made between the free wake lifting surface model and the skewed wake correction model used in BEM theory for the induced velocity on blade at different azimuth positions. The correction model for yawed flow in BEM theory seems to overpredict the induced velocity variations. The skewed wake induction in yawed condition causes a phase shift of angle of attack variation as a function of azimuth angle, particularly on the outboard of the blade. In addition, the blade aeroelastic deformations are found to further change the phase of circumferential distribution of aerodynamic loads. Rotor moments are influenced by the phase shifts of aerodynamic loads.Wind turbines operate in atmospheric shear layer and often in yawed flow condition, which, among others, produce cyclic fluctuating loads on the blades. The unsteady aerodynamics of wind turbine in both shear and yawed wind are studied in the present work. The rotor aeroelastic behaviors considering blade flexibility are also discussed. An advanced aeroelastic model based on free wake lifting surface model and geometrically exact beam theory is established to conduct the study. The aerodynamic simulations show that the wake is asymmetric in both shear and yawed conditions. Comparison is made between the free wake lifting surface model and the skewed wake correction model used in BEM theory for the induced velocity on blade at different azimuth positions. The correction model for yawed flow in BEM theory seems to overpredict the induced velocity variations. The skewed wake induction in yawed condition causes a phase shift of angle of attack variation as a function of azimuth angle, particularly on the outb...

Reduced-order modelling of wind turbine airfoil unsteady aerodynamic loading

In this paper, three different reduced-order models (auto-regressive and moving average, Volterra series and a surrogate-based recurrence framework model) are presented for the prediction of the unsteady dynamic loading of wind turbine airfoils. A wind turbine blade section can experience unsteady aerodynamic loads when subjected to an unsteady aerodynamic environment. The generations of three reduced-order models for the evaluation of unsteady aerodynamic loads are investigated, with the different models used as a representation of linear or non-linear loading. The validity of the presented reduced-order models is assessed mainly by comparing the model output with unsteady time-accurate computational fluid dynamics (CFD) simulations. The results reveal an encouraging agreement between the computational fluid dynamics simulations and the model predictions under different conditions. All three reduced-order models would therefore be useful in engineering conditioning for aeroelastic analysis and wind turbine design optimization.