發展黏性耦合三維小板法於風力發電機氣動力分析

The development of a viscous-coupled 3D panel method for the aerodynamic analysis of wind turbines

范秉天(Bryan Steven Nelson)

指導教授 ： 郭真祥

國立臺灣大學/工學院/工程科學及海洋工程學研究所/博士(2017年)

https://doi.org/10.6342/NTU201800594

摘要

無資料

關鍵字

計算流體力學 ； 三維小板法 ； 邊界層流離 ； 風力機

並列摘要

In addition to the many typical failure mechanisms that afflict wind turbines, units in Taiwan are also susceptible to catastrophic failure from typhoon-induced extreme loads. A key component of the strategy to prevent such failures is a fast, accurate aerodynamic design and analysis tool through which a fuller understanding of the aerodynamic loads acting on the units may be derived. Present modelling approaches range from low fidelity, such as the Blade Element Momentum (BEM) theory, to high fidelity, such as Navier-Stokes (NS) solvers. The former is fast and computationally inexpensive, but limited in terms of flow conditions which may be modelled, while the latter are very computationally expensive, and therefore impractical for design work.
To this end, a viscous-coupled 3D panel method is herewith proposed, which introduces a novel approach to simulating the severe flow separation so prevalent around wind turbine rotors. The Hess–Smith panel method was adopted for the inviscid calculations, and an empirically based boundary layer analysis is then performed to determine the separation point. The separated thick wake is then modelled as an extension of the surface geometry along which a constant pressure distribution is assumed. The wake geometry is determined iteratively, and an outer iterative loop is run to update the location of the separation point.
As proof of concept, the proposed method was first validated against experimental and numerical results for several high thickness wind turbine airfoils. At low angles of attack, pressure data predicted by the current method showed excellent agreement with the experimental data, as well as with the referenced numerical data, computed by an NS solver. At higher angles of attack, the current method showed reasonable agreement with the experimental data, while the referenced numerical data significantly overestimated the pressure distribution along the suction surface.
The ability of the current method to simulate the more complicated case of a rotating 3D wind turbine rotor was then assessed by code-to-code comparison with RANS data for a commercial 2 MW wind turbine. Along the outboard and inboard regions of the rotor, pressure distributions predicted by the current method showed very good agreement with the RANS data, while pressure data along the midspan region were slightly more conservative. The power curve predicted by the current method was correlated very well with that provided by the turbine manufacturer.
Taking into account the high degree of comparability with the more sophisticated RANS solver, the excellent agreement with the official data, and the considerably reduced computational expense, the author believes the proposed method could be a powerful standalone tool for the design and analysis of wind turbine blades.

並列關鍵字

CFD ； 3D panel method ； boundary layer separation ； wind turbine

參考文獻

[1] Ainslie, J. F., Calculating the flowfield in the wake of wind turbines, Journal of Wind Engineering and Industrial Aerodynamics, 1988; 27: 213-224.

[11] Churchfield, M.J., Lee, S., Michalakes, J., Moriarty, P.J., A numerical study of the effects of atmospheric and wake turbulence on wind turbine dynamics, J. Turbul. 2012, 13, 1–32.

[13] Cook, J., Nuccitelli, D., Green, S. A., Richardson, M., Winkler, B., Painting, R., Way, R., Jacobs, P., and Skuce, A., Quantifying the consensus on anthropogenic global warming in the scientific literature, Environmental Research Letters, 8–2, 2013.

[15] Deardorff, J. W., A numerical study of three-dimensional turbulent channel flow at large Reynolds numbers, J. Fluid Mech. 41, 453, 1970.

[17] Drela, M., and Giles, M. B., Viscous-Inviscid Analysis of Transonic and Low Reynolds Number Airfoils, AIAA Journal, 25(10), pp. 1347 – 1355, 1987.