Abstract
Wind turbines are often sited on different topographical features. In the current work, we performed wind-tunnel measurements of the wake behind a single wind turbine sited on two escarpments differing in the windward side shape using tomographic particle-image velocimetry. The escarpments are classified as forward facing step (FFS) and ramp-shape. The turbine sited on the FFS experiences an inflow with high flow shear and turbulence due to flow separation from the escarpment leading edge compared to the one on the ramp-shaped escarpment. As a consequence, the wake characteristics behind the turbine are strongly affected by the shape of the topography. The velocity deficit in the wake of the turbine is relatively higher in the forward facing step shape, but it also shows a faster recovery. The rotation of the wake is stronger for the turbine on the ramp-shaped escarpment, whereas the meandering of the wake is higher for the FFS case. The spatial coherence is observed to be higher in the near wake of the turbine sited on the FFS escarpment, while it is very similar in the far wake for both cases. Instantaneous vortices identified by the Q-criterion show that the development of tip and hub vortices is affected by the topography as well.
Highlights
Wind turbine wakes are characterized by highly complex three-dimensional flows due to the effects of boundary-layer flow shear, rotor rotation and multiple sources of vortex generation [1,2]
The spatial coherence is observed to be higher in the near wake of the turbine sited on the forward facing step (FFS) escarpment, while it is very similar in the far wake for both cases
The two topographies induced different levels of flow shear and turbulence which eventually had a strong influence on the wake characteristics of the turbine sited on them
Summary
Wind turbine wakes are characterized by highly complex three-dimensional flows due to the effects of boundary-layer flow shear, rotor rotation and multiple sources of vortex generation [1,2]. The development of these wakes is further dependent on different atmospheric conditions: thermal stratification, turbulence intensity and Coriolis force, to name a few [3,4,5,6]. The information on the three-dimensional evolution of the wind turbine wakes can be useful for accurate estimation of the flow experienced by downstream wind turbines This can facilitate the optimization of the turbine placement in a wind farm and provide basis for accurate power and load predictions. The most common laboratory measurement techniques, such as hotwire anemometry, laser-doppler velocimetry and two-component or stereoscopic particle-image velocimetry (PIV), only provide point or planar measurements
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
