Large scale dynamics of wind turbine wakes
by Dr. Juan José Trujilo, Colombia (PPRE 2002/03)
Dr. Juan José Trujilo finally finished his PhD thesis titled ‘Large scale dynamics of wind turbine wakes’ at University of Oldenburg / Forwind Institute last year, when he is also joined the German Wind Energy Institute in Wilhelmshaven (DEWI) near Oldenburg.
Summary of his PhD
The accurate simulation of the inflow of wind turbines operating in wake is of great interest at present. Specifically, the dynamic and in-homogeneous field in front of the turbines has complex effects on the dynamic loads and power.
A concept to approach the simulation of such inflow from an engineering perspective is the so-called wake-meandering modelling. The well established dynamic wake meandering model (DWM) assumes that the wake dynamics can be separated into two main processes. Namely, the development of the wake by small scale turbulence, and the meandering itself driven by large scale
turbulence. The validity of these assumptions could be demonstrated with the new full-field measurement techniques developed during this research. They have been applied in several measurement campaigns to capture large-scale wake dynamics with lidar.
The results suggest that the wake can be assumed to be transported passively in lateral and vertical direction by the large scales in the atmosphere. The assumption of frozen wake transport is found to be inaccurate, therefore an alternative approach, the extended-disk particle model (EDPm), has been proposed to cope with this limitation. It lets the deficits travel with independent speed. The transport is calculated with a stochastic-dispersion model that allows the parametrisation of near neutral to unstable atmospheric conditions. Simulations have been performed with a dynamic implementation showing satisfactory results.