Investigation of wind turbine wakes subjected to helicoidal perturbations

Details

Supervisors

Chatelain, Philippe ; Duponcheel, Matthieu

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil mécanicien, à finalité spécialisée

Abstract

enWind farms, despite their advantages, face a major challenge. As the first row of turbines extracts energy from the flow, it generates a region of reduced velocity downstream, referred to as the wake. This significantly limits the power production of downstream turbines, reducing the overall efficiency of the wind farm. To mitigate this effect, helix control strategies use individual pitch control (IPC) to create a rotation of the thrust application point around the rotor center, either in a clockwise (CW) or counter-clockwise (CCW) direction, giving the wake a helicoidal shape. While the effectiveness of helix control has been demonstrated in many studies, the physical mechanisms underlying its performance remain not fully understood. This Master’s thesis aims to fill this gap using Large Eddy Simulations combined with a simplified force model. The analysis shows that IPC-induced normal force produces an uneven velocity deficit in the wake. This deficit generates induced velocities, which in turn trigger specific flow mechanisms that result in the formation of a counter-rotating vortex pair (CVP) in both helix. This CVP appears to explain the improved performance of helix control through two effects: a radial deflection of the wake and an accelerated recovery of the velocity deficit. We observe an interaction between the swirl and the CCW helix, leading to a different CVP orientation compared to the CW case, which could explain the better performance of the CCW helix.