Some observations on wake redirection techniques of tandem wind turbines

A world-wide increase in demand for wind energy has seen an increase in the need for optimization of wind farms. In a wind farm arrangement, the upstream turbines have several negative effects on the downstream turbines. The upstream turbine extracts majority of energy from the flow, reducing the power output from the downstream turbine and exerts uneven loads on the downstream turbine. Wake redirection techniques, specifically yaw-misalignment, could mitigate these and possibly improve the overall power output of a wind farm. Smoke visualization, hot-wire anemometry, and force measurements were conducted in wind tunnels on a tandem scaled-down wind turbine setup to better understand the wake dynamics when the upstream turbine is yawed away from the incoming flow. Measurements indicate that the larger the yaw angle on the upstream turbine, the greater the wake deflection and the relation between the yaw angle and wake deflection angle appears to be linear. Moreover, these wake redirection dynamics decreased the side force and side toppling moment on the downstream turbine, which were not commonly measured in the literature, suggesting that yawing the upstream turbine is also beneficial to reducing the undesirable loads on the downstream turbine.