Empirical modeling of single‐wake advection and expansion using full‐scale pulsed lidar‐based measurements. (1st September 2014)

• Record Type: Journal Article
• Authors: Machefaux, E.; Larsen, G. C.; Troldborg, N.; Gaunaa, M.; Rettenmeier, A.
• Is Part Of: Wind energy. Volume 18:Number 12(2015)
• Page Start: 2085
• Page End: 2103
• Publication Date: 2014-09-01
• Subjects: wake meandering -- wake expansion -- wake advection -- turbulence -- lidar -- CFD -- large eddy simulation -- actuator line technique -- vortex cylinder -- spherical Hill's vortex; Wind power -- Periodicals; 621.312136
• DOI: 10.1002/we.1805
• Languages: English
• ISSNs: 1095-4244

Abstract

Abstract: In the present paper, single‐wake dynamics have been studied both experimentally and numerically. The use of pulsed lidar measurements allows for validation of basic dynamic wake meandering modeling assumptions. Wake center tracking is used to estimate the wake advection velocity experimentally and to obtain an estimate of the wake expansion in a fixed frame of reference. A comparison shows good agreement between the measured average expansion and the Computational Fluid Dynamics (CFD) large eddy simulation–actuator line computations. Frandsen's expansion model seems to predict the wake expansion fairly well in the far wake but lacks accuracy in the outer region of the near wake. An empirical relationship, relating maximum wake induction and wake advection velocity, is derived and linked to the characteristics of a spherical vortex structure. Furthermore, a new empirical model for single‐wake expansion is proposed based on an initial wake expansion in the pressure‐driven flow regime and a spatial gradient computed from the large‐scale lateral velocities, and thus inspired by the basic assumption behind the dynamic wake meandering model. Copyright © 2014 John Wiley & Sons, Ltd.