Actuator line simulations of a Joukowsky and Tj?reborg rotor using spectral element and finite volume methods

The Science of Making Torque from Wind

Kleusberg, E.^1 ; Sarmast, S.^2 ; Schlatter, P.^1 ; Ivanell, S.^1,2 ; Henningson, D.S.^1

Linné FLOW Centre and Swedish E-Science Research Centre (SeRC), KTH Mechanics, Royal Institute of Technology, Stockholm

SE-100 44, Sweden^1

Uppsala University, Wind Energy Section, Campus Gotland, Visby

SE-621 67, Sweden^2

关键词: Domain differences;    Finite volume code;    Numerical dissipation;    Onset of instabilities;    Optimal operating conditions;    Spectral element;    Spectral element method;    Wind turbine blades;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/753/8/082011/pdf
DOI  :  10.1088/1742-6596/753/8/082011

来源: IOP

【 摘 要 】

The wake structure behind a wind turbine, generated by the spectral element code Nek5000, is compared with that from the finite volume code EllipSys3D. The wind turbine blades are modeled using the actuator line method. We conduct the comparison on two different setups. One is based on an idealized rotor approximation with constant circulation imposed along the blades corresponding to Glauert's optimal operating condition, and the other is the Tjffireborg wind turbine. The focus lies on analyzing the differences in the wake structures entailed by the different codes and corresponding setups. The comparisons show good agreement for the defining parameters of the wake such as the wake expansion, helix pitch and circulation of the helical vortices. Differences can be related to the lower numerical dissipation in Nek5000 and to the domain differences at the rotor center. At comparable resolution Nek5000 yields more accurate results. It is observed that in the spectral element method the helical vortices, both at the tip and root of the actuator lines, retain their initial swirl velocity distribution for a longer distance in the near wake. This results in a lower vortex core growth and larger maximum vorticity along the wake. Additionally, it is observed that the break down process of the spiral tip vortices is significantly different between the two methods, with vortex merging occurring immediately after the onset of instability in the finite volume code, while Nek5000 simulations exhibit a 2-3 radii period of vortex pairing before merging.