Experiments in the wind turbine far wake for the evaluation of analytical wake models

Abstract

Nowadays, not only the size of single wind turbines but also the size of wind farms is increasing. Understanding the interaction between the turbines and especially the wake formed behind them are getting more important to further improve such wind turbine arrays. Consequently, new issues in wind energy research arise. An experimental wind tunnel study was conducted, in order to analyze and understand the far wake of a wind turbine. The experimental results were used to test if an analytical wake model derived by H. Schilichting for blunt bodies can be used to describe the velocity and width development in the far wake of wind turbines.Additionally, three analytical models for turbulence intensity were studied in order to investigate the turbulence intensity development downstream the turbine. The results of the evaluation show that the wake of a wind turbine agrees fairly well with the model according to Schlichting. The velocity deficit as well as the width in the wake behind the turbine, are found to deviate with around only 2% from the results obtained when the analytical model is applied. More spread results are obtained regarding the turbulence intensity predictions, however, accurate results can be achieved. Thus, it can be concluded that analytical wake models are well suited to estimate the velocity deficit, the width development and the turbulence intensity in the far wake of a wind turbine.