Influence of free-stream turbulence on the boundary layer stability of a wind turbine airfoil and near wake

Publication date
2023
Document type
Research article
Author
Fava, Thales C. L.
Lobo, Brandon A.
Nogueira, P. A. S.
Schaffarczyk, Alois P.
Henningson, Dan S.
Hanifi, Ardeshir
Organisational unit
DOI
URI
Series or journal
Journal of Physics: Conference Series
Periodical volume
2505(2023)
Periodical issue
012002
First page
1
Last page
10
Peer-reviewed
✅
Part of the university bibliography
✅
Keyword
Transition
Turbulence
Stability
Abstract
Free-stream turbulence (FST) alters the boundary layer of wind turbine blades, changing the hydrodynamic stability and near wake. Large-eddy simulations (LES) of a blade section with a laminar separation bubble for several turbulence intensities (TI) and a Reynolds number of 10^5 are performed. The effects of boundary-layer streaks generated by FST on Tollmien-Schlichting (TS) and Kelvin-Helmholtz (KH) instabilities are analyzed with a model based on the parabolized stability equations (PSE). Two competing effects on flow stability are identified. The spanwise-averaged mean-flow distortion stabilizes primary TS/KH modes forincreasing TI. However, this contribution seems dominant only for TI ≥ 8.6%. For lower TI, the spanwise-oscillating distortion caused by streaks destabilizes the flow, and the growth rates of secondary modal instabilities increase with the streak amplitude. The destabilization occurs mainly at spanwise locations with negative streaks since the inflection point shifts away from the wall, enhancing inviscid instabilities. Inflection points in the spanwise direction formed by the streaks also contribute to the destabilization. The modal structures from PSE and LES agree. Finally, the trailing-edge near-wake coherent structures are more energetic for TI ≥ 8.6% due to the partial stabilization of modal instabilities, delaying the turbulent breakdown.
Description
Open Access
Cite as
Journal of Physics: Conference Series 2505 (2023) 012002
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