On the Stability and Transition to Turbulence of the Flow over a Wind-Turbine Airfoil under Varying Free-Stream Turbulence Intensity

Publication date
2022
Document type
Conference paper
Author
Fava, Thales C. L.
Lobo, Brandon A.
Schaffarczyk, Alois P.
Hanifi, Ardeshir
Henningson, Dan S.
Organisational unit
URL
URI
Conference
12th International Symposium on Turbulence and Shear Flow Phenomena (TSFP12) Osaka, Japan (Online), July 19-22, 2022
Book title
12th International Symposium on Turbulence and Shear Flow Phenomena (TSFP12)
First page
1
Last page
6
Peer-reviewed
✅
Part of the university bibliography
✅
Abstract
The present work investigates the laminar-turbulent transition of the flow around a typical section of a wind turbine blade under different levels of isotropic inflow turbulence at a Reynolds number of Rec = 10^5 . Wall-resolved large-eddy simulations are performed under different turbulence intensities (TI) up to TI = 2.8 %. The results are analyzed with tools based on the linear stability and optimal-perturbation theory. At TI = 0%, transition to turbulence via the breakdown of Kelvin-Helmholtz (KH) rolls formed over the laminar separation bubble (LSB) is seen. These modes start to grow upstream of the LSB as an inflectional instability. At TI = 1.4 % rolls are also seen; but, instabilities formed by the interaction between streaks and the LSB also contribute to transition. The streaks are estimated to have a spanwise wavenumber around β = 100 ( β δ = 0.19 at 20 % chord; δ is the displacement thickness) and a frequency in the range f = 5 − 8 (f δ ∗ /ue = (1.4 − 2.3) × 10^−2 at 40 % chord; ue is the boundary layer edge velocity), close to that of the shear-layer instability. In the T I = 2.8 % case, the flow is heavily influenced by the presence of streaks, which stabilize the flow concerning inflectional/KH instabilities, but, at the same time, undergoes varicose-type instabilities and breakdown to turbulence.
Cite as
Fava et al. (2022) 12th Int. Symp. on Turbulence and Shear Flow Phenomena (TSFP-12)
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