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 language | American English |
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Number of pages | 13 |
DOIs | |
State | Published - 2018 |
Event | Wind Energy Symposium, 2018 - Kissimmee, United States Duration: 8 Jan 2018 → 12 Jan 2018 |
Conference
Conference | Wind Energy Symposium, 2018 |
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Country/Territory | United States |
City | Kissimmee |
Period | 8/01/18 → 12/01/18 |
Bibliographical note
See NREL/CP-5000-70686 for preprintNREL Publication Number
- NREL/CP-5000-71324
Keywords
- modeling
- wake skew
- wind energy
- wind turbine wakes