Abstract
In this work, an in-depth study has been made to examine the benefits of span-wise placed horizontal axis wind turbine configurations. The model turbine rotors have similar configurations with a sectional profile of SG6043, and are tested at low tip speed ratio conditions. The study has been performed for the two span-wise placed rotors having tip-to-tip separation distances of 1R (R being the rotor radius) and 0.5R, and are analyzed within the near-wake regime. The wind turbine wake assessment has been carried out in an open circuit wind tunnel with the help of a constant temperature hotwire anemometry. The downstream velocity deficit assessment shows that the wake of closely placed turbines undergoes faster interaction at short downstream distances, where the whole wake is characterized as an array of localized high velocity-deficit regions associated with each rotor. However, as the wake moves downstream, the rotor wakes start interacting with each other until they eventually form a single wake. The wake recovery rate of the span-wise placed rotors is enhanced by the increase of rotor spacing and wind speed. Furthermore, the tip of the blade generates helical vortices due to which a tangential component of velocity is added in the stream velocity vector. This gives velocity greater than stream velocity in ± 0.75R to ± 1.25R along a lateral direction with respect to wake centre.
