2 research outputs found
Maximizing wind farm power output with the helix approach -- experimental validation and wake analysis using tomographic PIV
Wind farm control can play a key role in reducing the negative impact of
wakes on wind turbine power production. The helix approach is a recent
innovation in the field of wind farm control, which employs individual blade
pitch control to induce a helical velocity profile in a wind turbine wake. This
forced meandering of the wake has turned out to be very effective for the
recovery of the wake, increasing the power output of downstream turbines by a
significant amount. This paper presents a wind tunnel study with two scaled
wind turbine models, of which the upstream turbine is operated with the helix
approach. We used tomographic particle image velocimetry to study the dynamic
behavior of the wake under influence of the helix excitation. The measured flow
fields confirm the wake recovery capabilities of the helix approach compared to
normal operation. Additional emphasis is put on the effect of the helix
approach on the breakdown of blade tip vortices, a process that plays an
important role in re-energizing the wake. Measurements indicate that the
breakdown of tip vortices, and the resulting destabilization of the wake is
enhanced significantly with the helix approach. Finally, turbine measurements
show that the helix approach was able to increase the combined power for this
particular two turbine setup by as much as 15%.Comment: Submitted to Wind Energ
Burden and attitude to resistant and refractory migraine
Background: New treatments are currently offering new opportunities and challenges in clinical management and research in the migraine field. There is the need of homogenous criteria to identify candidates for treatment escalation as well as of reliable criteria to identify refractoriness to treatment. To overcome those issues, the European Headache Federation (EHF) issued a Consensus document to propose criteria to approach difficult-to-treat migraine patients in a standar