Analysis of the effect of a series of back twist blade configurations for an active pitch-to-stall floating offshore wind turbine

Dawn Ward, Maurizio Collu, Joy Sumner

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)
9 Downloads (Pure)


For a turbine mounted on a floating platform, extreme induced loads can be increased by up to 1.6 times those experienced by a turbine situated on a fixed base. If these loads cannot be reduced, towers must be strengthened which will result in increased costs and weight. These tower loads would be additionally exasperated for a pitch-to-feather controlled turbine by a phenomenon generally referred to as "negative damping," if it were not avoided. Preventing negative damping from occurring on a pitch-to-feather controlled floating platform negatively affects rotor speed control and regulated power performance. However, minimizing the blade bending moment response can result in a reduction in the tower fore-aft moment response, which can increase the tower life. A variable-speed, variable pitch-to-stall (VSVP-S) floating semi-submersible wind turbine, which does not suffer from the negative damping and hence provides a more regulated power output, is presented. This incorporates a back twist blade profile such that the blade twist, starting at the root, initially twists toward stall and, at some pre-determined "initiation" point, changes direction to twist back toward feather until the tip. Wind frequency weighting was applied to the tower axial fatigue life trends of different blade profiles and a preferred blade back twist profile was identified. This had a back twist angle of -3 deg and started at 87.5% along the blade length and achieved a 5.1% increase in the tower fatigue life.

Original languageEnglish
Article number062001
Number of pages9
JournalJournal of Offshore Mechanics and Arctic Engineering
Issue number6
Early online date8 Apr 2020
Publication statusPublished - 1 Dec 2020


  • blade back twist
  • design of offshore structures
  • dynamics of structures
  • floating and moored production systems
  • floating offshore wind turbine (FOWT)
  • ocean energy technology
  • pitch-to-stall
  • structural mechanics and foundation
  • tower axial fatigue life


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