TITLE:
On the Wake Flow Interaction between Model Turbines with Varying Streamwise Distance
AUTHORS:
Mubashar Khan, Ylva Odemark, Mats Sandberg, Jens H. M. Fransson
KEYWORDS:
Wind Turbine Model, Perforated Disc, Wake Flow Interaction, Particle Image Velocimetry, Pressure Footprint
JOURNAL NAME:
Open Journal of Fluid Dynamics,
Vol.7 No.4,
December
19,
2017
ABSTRACT:
Wind tunnel measurements using particle image velocimetry have been performed around two perforated discs, with varying streamwise distance, in order to simulate the wake interaction between wind turbines. The static pressure footprint (p-f) on ground level associated with the wake behind the disc and wake velocity data for both the streamwise and wall-normal velocity components with the corresponding turbulence intensities are reported. The p-f method shows that the size of the wake regions, behind the wind turbine models, initially drop when a second disc is placed just downstream of the first one. From a mutual distance (Δ χ) of about five disc diameters (5D), both wake footprints increase as the mutual distance is increased, and for very large mutual distances, approximately Δ χ/ D > 15, the footprint of the downstream disc has recovered and is about the same as for a single disc. At last we conclude that despite very different inlet conditions to the discs, with about 50% of reduced velocity on the centre line upstream of the second disc and an increase of the maximum streamwise fluctuations by 90%, the mean velocities in the wake are proven to scale with the hub height velocity.