Large Eddy Simulations of Curled Wakes from Tilted Wind Turbines

25 Pages Posted: 28 Jun 2021

See all articles by Hannah M. Johlas

Hannah M. Johlas

University of Massachusetts Amherst

David P. Schmidt

University of Massachusetts Amherst

Matthew A. Lackner

University of Massachusetts Amherst

Date Written: 2021

Abstract

One control strategy to increase power production in wind farms is angling wind turbine rotors, in order to steer wakes away from downwind turbines. Although rotor yaw is the most common approach to wake steering, tilting the rotor vertically to steer the wake downward can also increase total farm power. In this study, large eddy simulations of a 15 MW turbine are performed for rotor tilt angles of 0°, 15°, and 30° with below-rated turbulent inflow. Wake characteristics are analyzed, including using circulation to quantify the curled wake's counter-rotating vortex pair and quantifying wake shapes by fitting Legendre polynomials to wake edge polar coordinates. Tilting the rotor causes downward wake steering, shorter and wider wake cross-sections, and stronger counter-rotating vortices. Although the wake velocity deficit recovers similarly for tilted and non-tilted wakes, the power available to a downwind rotor recovers faster because the tilted wake is steered away from the downwind rotor area and is replaced by high-speed air from above. This also causes higher effective wind shear across the downwind rotor. Additional simulations double the gap between the ground surface and the rotor bottom, which affects the wake geometry as well as the downwind power recovery and wind shear.

Suggested Citation

Johlas, Hannah M. and Schmidt, David P. and Lackner, Matthew A., Large Eddy Simulations of Curled Wakes from Tilted Wind Turbines (2021). Available at SSRN: https://ssrn.com/abstract=3875189 or http://dx.doi.org/10.2139/ssrn.3875189

Hannah M. Johlas (Contact Author)

University of Massachusetts Amherst

Department of Operations and Information Managemen
Amherst, MA 01003
United States

David P. Schmidt

University of Massachusetts Amherst

Department of Operations and Information Managemen
Amherst, MA 01003
United States

Matthew A. Lackner

University of Massachusetts Amherst

Department of Operations and Information Managemen
Amherst, MA 01003
United States

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