Effect of freestream turbulence on the coherent dynamics of a wind turbine wake
File(s)
Author(s)
Biswas, Neelakash
Buxton, Oliver
Type
Journal Article
Abstract
The wake of a model wind turbine exposed to incoming freestream turbulence (FST) with a variety of turbulent characteristics is studied through Particle Image Velocimetry experiments. The FST cases were produced using different passive turbulence generating grids. The cases spanned turbulent intensities (Ti) in the range 1.3% ≲ Ti ≲ 14% and only considered short integral length scales Lv ≲ 0.2D (where D is the turbine diameter). Increasing Ti and Lv in this range resulted in an earlier breakdown of the tip vortices which is shown to be associated with increased wake meandering amplitudes. For all the FST cases considered, the initiation of wake meandering was found to be related to a turbine instability that is excited by the nacelle’s shedding, even for the highest FST levels. The amplitudes of wake meandering were similar for all the cases in the near wake (x < 2D), but the amplitudes in the far wake (x > 4D) were discernibly higher for all the FST cases compared to the no grid case (lowest Ti), primarily due to the early break down of the tip vortices. Deeper insights into the origins, and subsequent evolution, of the various coherent motions (characterised by particular frequencies) in the presence of FST are obtained through analysis of the multi-scale triple-decomposed coherent kinetic energy budgets. The wake meandering modes in the presence of FST are shown to better utilize the mean velocity shear, extracting more energy from the mean flow while other sources such as non-linear triadic interactions and diffusion also become important
Date Issued
2026-06-25
Date Acceptance
2026-05-05
Citation
Journal of Fluid Mechanics, 2026, 1037
ISSN
0022-1120
Publisher
Cambridge University Press
Journal / Book Title
Journal of Fluid Mechanics
Volume
1037
Copyright Statement
© The Author(s), 2026. Published by Cambridge University Press. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.
License URL
Identifier
10.1017/jfm.2026.11665
Subjects
vortex dynamics
vortex shedding
wakes
Publication Status
Published
Article Number
A3
Date Publish Online
2026-06-11