Experimental Investigation on the Effect of Lateral Turbine Spacing on Interactions of Wakes

Abstract

In recent years, development in wind energy has put great attention on the manifold possibilities of increasing wind farm efficiencies. Motivated by multiple positive effects dualrotors promise at controlling and mitigating wakes, it is goal of this work to gain experimental insight on the characteristics of a double-rotor wake in dependency of the lateral spacing between the turbines. Additionally, the influence of the rotational direction of the model wind turbine showed to be of great relevance and will be studied under laminar inflow conditions between 4 - 7 ms-1. An array of 21 hot-wires at a sampling frequency of 6 kHz will be traversing until 8 D downstream of the double rotor plane to allow for one- and two-point statistics in the wake interaction region. It will be presented that both lateral distance and direction of rotation has great effect on the entrainment of undisturbed air into the dual wake. In terms of turbine control, decreasing the lateral distance increases the generated power by 4-9%. The knowledge on turbulence structures and their decay in the mixing area could be used to adapt, optimise and implement control strategies in wind farms for a better entrainment and thus an overall quicker wake recovery.