Wind farm global blockage as an adverse pressure gradient problem: turbulence amplification and spectral modification in the induction region of a model wind farm
Abstract
The induction region of a model wind farm is investigated experimentally as an adverse pressure gradient (APG) turbulent boundary layer problem, using hot-wire anemometry. An array of porous discs, with diameter D=50\,mm representing the farm, in multiple configurations across two turbulent boundary layers of different depths, with farm-present and farm-absent configurations compared throughout. The farm imposes a spatially developing adverse pressure gradient in the approach flow. Spanwise-averaged measurements reveal systematic farm-scale global blockage extending to at least 10D upstream in all cases. The farm-induced turbulence intensity increase, which reaches up to 7% relative to the farm-absent reference for the shallowest boundary layer, is shown by cumulative variance decomposition to be carried predominantly by large-scale motions of the boundary layer, whilst the small-scale turbulence intensity is only weakly affected. This selective large-scale energisation is consistent with the outer-layer amplification driven by an adverse pressure gradient. The concentration of farm-induced turbulence energy at scales comparable to or larger than the rotor diameter has direct implications for turbine fatigue loading, preferentially exciting coherent rotor-scale load fluctuations at the frequencies most damaging under fatigue. The results establish a quantitative link between wind farm global blockage and APG boundary layer physics.
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BibTeX
@misc{mcglade2026wind,
title = {{Wind farm global blockage as an adverse pressure gradient problem: turbulence amplification and spectral modification in the induction region of a model wind farm}},
author = {Adrian T. McGlade and Oliver R. H. Buxton},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.26415},
eprint = {2609.26415},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.26415},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Wind farm global blockage as an adverse pressure gradient problem: turbulence amplification and spectral modification in the induction region of a model wind farm
AU - Adrian T. McGlade
AU - Oliver R. H. Buxton
PY - 2026
DA - 2026/09/22
PB - arXiv
DO - 10.48550/arxiv.2609.26415
UR - https://arxiv.org/abs/2609.26415
AB - The induction region of a model wind farm is investigated experimentally as an adverse pressure gradient (APG) turbulent boundary layer problem, using hot-wire anemometry. An array of porous discs, with diameter D=50\,mm representing the farm, in multiple configurations across two turbulent boundary layers of different depths, with farm-present and farm-absent configurations compared throughout. The farm imposes a spatially developing adverse pressure gradient in the approach flow. Spanwise-averaged measurements reveal systematic farm-scale global blockage extending to at least 10D upstream in all cases. The farm-induced turbulence intensity increase, which reaches up to 7% relative to the farm-absent reference for the shallowest boundary layer, is shown by cumulative variance decomposition to be carried predominantly by large-scale motions of the boundary layer, whilst the small-scale turbulence intensity is only weakly affected. This selective large-scale energisation is consistent with the outer-layer amplification driven by an adverse pressure gradient. The concentration of farm-induced turbulence energy at scales comparable to or larger than the rotor diameter has direct implications for turbine fatigue loading, preferentially exciting coherent rotor-scale load fluctuations at the frequencies most damaging under fatigue. The results establish a quantitative link between wind farm global blockage and APG boundary layer physics.
ER -