Improved Modeling of Wakes: Experimental Study and Experimentally Anchored Model

摘要

An accurate prediction of wake losses is required in order to be able to accurately estimate the expected annual energy yield for a given wind farm. In the present work, an improved wake model that is ten times more accurate than existing wake models is presented. The development of this model is accomplished by performing detailed flow measurements in the ETH Zurich Dynamically-Scaled Wind Turbine Test Facility under representative offshore flow conditions and near full-scale nondimensionals. The detailed flow field measurements, with a freestream turbulence intensity of 2.5%, show that the mixing layer primarily drives the evolution of the wake between the wake and the freestream. This observation is a key component of the experimentally anchored wake model that is developed to describe, using free shear flow theory, the evolution of the streamwise velocity in the wake. Within the wake, at a downstream distance of 6.5 rotor diameters, the predicted power from the new wake model differs by 4% compared to experiment; on the other hand, a conventional wake model has a difference of more than 30%.