On the Effects of Wind Turbine Wake Skew Caused by Wind Veer

Research output: Contribution to conferencePaperpeer-review

12 Scopus Citations

Abstract

Because of Coriolis forces caused by the Earth’s rotation, the structure of the atmospheric boundary layer often contains a wind-direction change with height, also known as wind-direction veer. Under low-turbulence conditions, such as a stably stratified atmosphere, this veer can be significant across the vertical extent of a wind turbine’s rotor disk. The veer then causes the wind turbine wake to skew as it advects downstream. This wake skew has been observed both experimentally and numerically. In this work, we attempt to examine the wake skewing process in some detail, and quantify how differently a skewed wake versus a nonskewed wake affects a downstream turbine. We do this by performing atmospheric large-eddy simulations to create turbulent inflow winds with and without veer. In the veer case, there is a roughly 8° wind-direction change across the turbine rotor. We then perform subsequent large-eddy simulations using these inflow data with an actuator line rotor model to create wakes. The turbine modeled is a large, modern, offshore, multimegawatt turbine. We examine the unsteady wake data in detail and show that the skewed wake recovers faster than the nonskewed wake. We also show that the wake deficit does not skew to the same degree that a passive tracer would if subject to veered inflow. Lastly, we use the wake data to place a hypothetical turbine 9 rotor diameters downstream by running aeroelastic simulations with the simulated wake data. We see differences in power and loads if this downstream turbine is subject to a skewed or nonskewed wake. We feel that the differences observed between the skewed and nonskewed wake are important enough that the skewing effect should be included in engineering wake models.

Original languageAmerican English
Number of pages13
DOIs
StatePublished - 2018
EventWind Energy Symposium, 2018 - Kissimmee, United States
Duration: 8 Jan 201812 Jan 2018

Conference

ConferenceWind Energy Symposium, 2018
Country/TerritoryUnited States
CityKissimmee
Period8/01/1812/01/18

Bibliographical note

See NREL/CP-5000-70686 for preprint

NREL Publication Number

  • NREL/CP-5000-71324

Keywords

  • modeling
  • wake skew
  • wind energy
  • wind turbine wakes

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