助力 “碳达峰，碳中和”——AMS风能专题服务生态文明建设
要通过创新驱动，实现我国从风能大国提升为风能强国的目标，必须解决面临的关键科学技术问题。2020年，AMS邀请美国爱荷华州立大学的胡辉教授和华北电力大学的王晓东教授共同组织发表了“Wind turbines: aeromechanics and farm optimization”风能专题，以促进风能技术这一领域的学术交流，推动风能科学与技术的进步。
Prof. Hui Hu
Iowa State University, USA
Prof. Xiaodong Wang
01
Metamodeling-based parametric optimization of DBD plasma actuation to suppress flow separation over a wind turbine airfoil model
https://link.springer.com/article/10.1007/s10409-020-00951-6
While dielectric-barrier-discharge (DBD) based plasma actuation systems have been successfully demonstrated to suppress massive flow separation over wind turbine blades to reduce the transient aerodynamic loadings acting on the turbine blades, it is still a non-trivial task to establish a best combination of various operating parameters for a DBD plasma actuation system to achieve the optimized flow control effectiveness. In the present study, a regression Kriging based metamodeling technique is developed to optimize the operating parameters of a DBD plasma actuation system for suppressing deep stall over the surface of a wind turbine blade section/airfoil model. The data points were experimentally obtained by embedding a nanosecond-pulsed DBD (NS-DBD) plasma actuator at the leading edge of the airfoil model. The applied voltage and frequency for the NS-DBD plasma actuation were used as the design variables to demonstrate the optimization procedure. The highest possible lift coefficient of the turbine airfoil model at deep stalled angles of attack (i.e., α = 22° and 24°) were selected as the objective function for the optimization. It was found that, while the metamodeling-based procedure could accurately predict the objective function within the bounds of the design variables with an uncertainty ~ 2%, a global accuracy level of ~ 97% was achieved within the whole design space.
02
Aerodynamic load control on a dynamically pitching wind turbine airfoil using leading-edge protuberance method
Y. N. Zhang, M. M. Zhang, C. Cai, J. Z. Xu
https://link.springer.com/article/10.1007/s10409-020-00939-2
The aerodynamic loads of wind turbine blades are substantially affected by dynamic stall induced by the variations of the angle of attack of local airfoil sections. The purpose of the present study is to explore the effect of leading-edge protuberances on the fluctuation of the aerodynamic performances for wind turbine airfoil during dynamic stall. An experimental investigation is carried out by a direct force measurement technique employing force balance at a Reynolds number Re = 2 × 10⁵. The phase-averaged and instantaneous aerodynamic loads of the pitching airfoil, including the baseline and the wavy airfoil, are presented and analyzed. The phase-averaged results indicate that the effects of dynamic stall for the wavy airfoil can be delayed or minimized compared to the baseline airfoil, and the negative damping area of the wavy airfoil is significant decreased in full-stall condition. These effects of leading-edge protuberances are more notable at a higher reduced frequency. For the instantaneous aerodynamic loads of the wavy airfoil, there is an observable reduction in fluctuations compared with baseline case. Furthermore, spectral analysis is applied to quantitatively undercover the nonstationary features of the instantaneous aerodynamic loads. It is found that the leading edge protuberances can reduce the harmonics of the aerodynamic force signal, and enhance the stability of the aerodynamic loads under different reduced frequencies. In conclusion, leading-edge protuberances are found effective to reduce the fluctuation characteristics of the aerodynamic loads during the dynamic stall process, and help to improve the stability and prolong the service life of the wind turbine blades.
03
Numerical studies of undulation control on dynamic stall for reverse flows
Biao Wang, Jian Liu, Yunjun Yang, Zhixiang Xiao
https://link.springer.com/article/10.1007/s10409-020-00950-7
The delayed detached-eddy simulation with adaptive coefficient (DDES-AC) method is used to simulate the baseline and leading-edge undulation control of dynamic stall for the reverse flow past a finite-span wing with NACA0012 airfoil. The numerical results of the baseline configuration are compared with available measurements. DDES and DDES-AC perform differently when predicting the primary and secondary dynamic stalls. Overall, DDES-AC performs better owing to the decrease of grey area between the strong shear layer and the fully three-dimensional separated flow. Moreover, the effects of the undulating leading-edge on the forces, lift gradients, and instantaneous flow structures are explored. Compared with the uncontrolled case, the lift gradient in the primary dynamic stall is reduced from 18.4 to 8.5, and the secondary dynamic stall disappears. Therefore, periodic unsteady air-loads are also reduced. Additionally, the control mechanism of the wavy leading edge (WLE) is also investigated by comparison with the straight leading edge (SLE). No sudden breakdown of strong vortices is the main cause for WLE control.
04
On the calibration of rotational augmentation models for wind turbine load estimation by means of CFD simulations
Belen Soledad Burgos Tafur, Elia Daniele, Bernhard Stoevesandt, Philipp Thomas
https://link.springer.com/article/10.1007/s10409-020-00949-0
In this work the improved version of an engineering model which accounts for rotational augmentation effects by means of computational fluid dynamics (CFD) calibration is explored and discussed. Based on an analysis of the NREL Phase VI wind turbine, the novel modeling is presented, which uses as base line the formulation proposed by Chaviaropoulos and Hansen. The model is calibrated based on CFD simulations using OpenFOAM. The corresponding correction of the two dimensional polars is straightforward implemented within MoWiT, an in-house software for load calculation. The novel formulation results in improved lift and drag coefficients prediction in all considered cases, reducing the deviation with respect to the rotating CFD cases down to few percent. The optimal configuration including the correction for tip effects of Shen shows better agreements at the very tip of the blade. Furthermore the range of applicability for large wind turbine rotor blades based on a virtual 10MW rotor model is discussed.
05
Unsteady aerodynamic characteristics of a horizontal wind turbine under yaw and dynamic yawing
Zhaoliang Ye, Xiaodong Wang, Ziwen Chen, Luyao Wang
https://link.springer.com/article/10.1007/s10409-020-00947-2
Horizontal axis wind turbine (HAWT) often works under yaw due to the stochastic variation of wind direction. Yaw also can be used as one of control methods for load reduction and wake redirection of HAWT. Thus, the aerodynamic performance under yaw is very important to the design of HAWT. For further insight into the highly unsteady characteristics aerodynamics of HAWT under yaw, this paper investigates the unsteady variations of the aerodynamic performance of a small wind turbine under static yawed and yawing process with sliding grid method, as well as the there-dimensional effect on the unsteady characteristics, using unsteady Reynolds-averaged Navier–Stokes (URANS) simulations. The simulation results are validated with experimental data and blade element momentum (BEM) results. The comparisons show that the CFD results have better agreement with the experimental data than both BEM results. The wind turbine power decreases according to a cosine law with the increase of yaw angle. The torque under yaw shows lower frequency fluctuations than the non-yawed condition due to velocity component of rotation and the influence of spinner. Dynamic yawing causes larger fluctuate than static yaw, and the reason is analyzed. The aerodynamic fluctuation becomes more prominent in the retreating side than that in the advancing side for dynamic yawing case. Variations of effective angle of attack and aerodynamic forces along the blade span are analyzed. The biggest loading position moves from middle span to outer span with the increase of yaw angle. Three-dimensional stall effect presents load fluctuations at the inner board of blade, and becomes stronger with the increase of yaw angle.
06
Snow-powered research on utility-scale wind turbine flows
Jiarong Hong, Aliza Abraham
https://link.springer.com/article/10.1007/s10409-020-00934-7
This paper provides a review of the general experimental methodology of snow-powered flow visualization and super-large-scale particle image velocimetry (SLPIV), the corresponding field deployments and major scientific findings from our work on a 2.5 MW utility-scale wind turbine at the Eolos field station. The field measurements were conducted to investigate the incoming flow in the induction zone and the near-wake flows from different perspectives. It has been shown that these snow-powered measurements can provide sufficient spatiotemporal resolution and fields of view to characterize both qualitatively and quantitatively the incoming flow, all the major coherent structures generated by the turbine (e.g., blade, nacelle and tower vortices, etc.) as well as the development and interaction of these structures in the near wake. Our work has further revealed several interesting behaviors of near-wake flows (e.g., wake contraction, dynamic wake modulation, meandering and deflection of the nacelle wake, etc.), and their connections with constantly-changing inflows and turbine operation, which are uniquely associated with utility-scale turbines. These findings have demonstrated that the near wake flows, though highly complex, can be predicted with substantial statistical confidence using supervisory control and data acquisition (SCADA) and structural response information readily available from current utility-scale turbines. Such knowledge can be potentially incorporated into wake development models and turbine controllers for wind farm optimization in the future.