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Title: Dissipation of turbulence in the wake of a wind turbine

The wake of a wind turbine is characterized by increased turbulence and decreased wind speed. Turbines are generally deployed in large groups in wind farms, and so the behaviour of an individual wake as it merges with other wakes and propagates downwind is critical in assessing wind-farm power production. This evolution depends on the rate of turbulence dissipation in the wind-turbine wake, which has not been previously quantified in field-scale measurements. In situ measurements of winds and turbulence dissipation from the wake region of a multi-MW turbine were collected using a tethered lifting system (TLS) carrying a payload of high-rate turbulence probes. Ambient flow measurements were provided from sonic anemometers on a meteorological tower located near the turbine. Good agreement between the tower measurements and the TLS measurements was established for a case without a wind-turbine wake. When an operating wind turbine is located between the tower and the TLS so that the wake propagates to the TLS, the TLS measures dissipation rates one to two orders of magnitude higher in the wake than outside of the wake. These data, collected between two and three rotor diameters D downwind of the turbine, document the significant enhancement of turbulent kinetic energymore » dissipation rate within the wind-turbine wake. These wake measurements suggest that it may be useful to pursue modelling approaches that account for enhanced dissipation. Furthermore. comparisons of wake and non-wake dissipation rates to mean wind speed, wind-speed variance, and turbulence intensity are presented to facilitate the inclusion of these measurements in wake modelling schemes.« less
Authors:
 [1] ;  [2]
  1. Univ. of Colorado, Boulder, CO (United States); National Renewable Energy Lab. (NREL), Golden, CO (United States)
  2. National Oceanic and Atmospheric Administration (NOAA), Boulder, CO (United States); Univ. of Colorado, Boulder, CO (United States)
Publication Date:
OSTI Identifier:
1220581
Report Number(s):
NREL/JA--5000-60690
Journal ID: ISSN 0006-8314
Grant/Contract Number:
AC36-08GO28308
Type:
Accepted Manuscript
Journal Name:
Boundary-Layer Meteorology
Additional Journal Information:
Journal Volume: 154; Journal Issue: 2; Related Information: Boundary-Layer Meteorology; Journal ID: ISSN 0006-8314
Publisher:
Springer
Research Org:
NREL (National Renewable Energy Laboratory (NREL), Golden, CO (United States))
Sponsoring Org:
Colorado Research and Education in Wind
Country of Publication:
United States
Language:
English
Subject:
17 WIND ENERGY wind energy; wind turbines; atmospheric boundary layer; turbulence; dissipation rate; tethered lifting system; turbulent kinetic energy