Floating wind turbines and a new transition to turbulence
In this seminar, wind tunnel experiments will be presented that aim to characterize the turbulent wakes of floating wind turbines. A major question for wind energy is how wake turbulence from wind turbines will develop and affect downstream wind turbines. The key question is which effects will dominate wake recovery. Floating wind turbines for the deep sea are of interest for the future of wind energy, which is why we are investigating floating wind turbines in wind tunnel tests. Using a motorized platform with 6 degrees of freedom, the movements from front to back (sway and pitch) and from side to side (sway and roll) can be investigated. We find that the wake recovery changes significantly when the turbine moves. Faster recovery is observed for movements with a Strouhal number of .4 to .6. The detailed investigation of the recovery leads to new insights into the transition to turbulence. The movement of the wind turbine leads to a change in the wake in which the turbulence is not fully developed. In particular, we find in the near wake a nonlinear growth of coherent structures that exhibit clear features of nonlinear dynamics such as quasi-periodic mode mixing. At a certain point downstream, these structures decay and lead to turbulence. The recovery in the distance seems to show a universal behavior. It therefore appears that the nonlinear dynamics shorten the transition to turbulence.
Contact Martin Obligado for more information or to schedule a discussion with the seminar speaker.