Turbulence within variable-size wind turbine arrays

Abstract

A wind tunnel experiment was performed to study turbulence processes within a model wind turbine array of 3 by 8 model wind turbines of alternating sizes placed aligned with the mean flow. The model wind farm was placed in a boundary layer developed over both smooth and rough surfaces under neutrally stratified conditions. Turbulence statistics, TKE budget terms, and the spectral structure of the turbulence generated within and above the wind farm reveal relevant information about the processes modulating the turbulent energy transfer from the boundary layer to the turbines. The results of the experiment suggest that heterogeneity in turbine size within a wind farm introduce complex flow interactions not seen in a homogeneous farm, and may have positive effects on turbulent loading on the turbines and turbulent exchange with the atmosphere. In general, large scale motions are heavily dampened behind the first row of turbines but a portion of such structures are generated far inside the wind farm, and the scale of the most energetic eddy motions was relatively consistent at different elevations. Overall, the experiment revealed the possibility that heterogeneity of wind turbine size within wind farms have the potential to change the overall potential to harvest energy from the wind, and alter the economics of a project.