title: Natural snowfall reveals large-scale flow structures in the wake of a 2.5-MW wind turbine.
abstract: To improve power production and structural reliability of wind turbines, there is a pressing need to understand how turbines interact with the atmospheric boundary layer. However, experimental techniques capable of quantifying or even qualitatively visualizing the large-scale turbulent flow structures around full-scale turbines do not exist today. Here we use snowflakes from a winter snowstorm as flow tracers to obtain velocity fields downwind of a 2.5-MW wind turbine in a sampling area of ~36 × 36 m(2). The spatial and temporal resolutions of the measurements are sufficiently high to quantify the evolution of blade-generated coherent motions, such as the tip and trailing sheet vortices, identify their instability mechanisms and correlate them with turbine operation, control and performance. Our experiment provides an unprecedented in situ characterization of flow structures around utility-scale turbines, and yields significant insights into the Reynolds number similarity issues presented in wind energy applications.
authors: 1] Saint Anthony Falls Laboratory, 2 Third Avenue, Minneapolis, Minnesota 55414, USA [2] Department of Mechanical Engineering, University of Minnesota, 111 Church Street SE, Minneapolis, Minnesota 55455, USA.
authors: Jiarong
authors: J
authors: Hong
authors: 1] Saint Anthony Falls Laboratory, 2 Third Avenue, Minneapolis, Minnesota 55414, USA [2] Department of Mechanical Engineering, University of Minnesota, 111 Church Street SE, Minneapolis, Minnesota 55455, USA.
authors: Mostafa
authors: M
authors: Toloui
authors: 1] Saint Anthony Falls Laboratory, 2 Third Avenue, Minneapolis, Minnesota 55414, USA [2] Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 West Green Street, Urbana, Illinois 61801, USA.
authors: Leonardo P
authors: LP
authors: Chamorro
authors: 1] Saint Anthony Falls Laboratory, 2 Third Avenue, Minneapolis, Minnesota 55414, USA [2] Department of Civil Engineering, University of Minnesota, 500 Pillsbury Drive SE, Minneapolis, Minnesota 55455, USA.
authors: Michele
authors: M
authors: Guala
authors: 1] Saint Anthony Falls Laboratory, 2 Third Avenue, Minneapolis, Minnesota 55414, USA [2] Department of Civil Engineering, University of Minnesota, 500 Pillsbury Drive SE, Minneapolis, Minnesota 55455, USA.
authors: Kevin
authors: K
authors: Howard
authors: Department of Mechanical Engineering, University of Minnesota, 111 Church Street SE, Minneapolis, Minnesota 55455, USA.
authors: Sean
authors: S
authors: Riley
authors: Saint Anthony Falls Laboratory, 2 Third Avenue, Minneapolis, Minnesota 55414, USA.
authors: James
authors: J
authors: Tucker
authors: 1] Saint Anthony Falls Laboratory, 2 Third Avenue, Minneapolis, Minnesota 55414, USA [2] Department of Civil Engineering, University of Minnesota, 500 Pillsbury Drive SE, Minneapolis, Minnesota 55455, USA.
authors: Fotis
authors: F
authors: Sotiropoulos