Going Beyond BEM with BEM: An Insight into Dynamic Inflow Effects on Floating Wind Turbines

Francesco Papi, Jason Jonkman, Amy Robertson, Alessandro Bianchini

Research output: Contribution to journalArticlepeer-review


Blade element momentum (BEM) theory is the backbone of many industry-standard wind turbine aerodynamic models. To be applied to a broader set of engineering problems, BEM models have been extended since their inception and now include several empirical corrections. These models have benefitted from decades of development and refinement and have been extensively used and validated, proving their adequacy in predicting aerodynamic forces of horizontal-axis wind turbine rotors in most scenarios. However, the analysis of floating offshore wind turbines (FOWTs) introduces new sets of challenges, especially if new-generation large and flexible machines are considered. In fact, due to the combined action of wind and waves and their interaction with the turbine structure and control system, these machines are subject to unsteady motion and thus unsteady inflow on the wind turbine's blades, which could put BEM models to the test. Consensus has not been reached on the accuracy limits of BEM in these conditions. This study contributes to the ongoing research on the topic by systematically comparing four different aerodynamic models, ranging from BEM to computational fluid dynamics, in an attempt to shed light on the unsteady aerodynamic phenomena that are at stake in FOWTs and whether BEM is able to model them appropriately. Simulations are performed on the UNAFLOW 1:75 scale rotor during imposed harmonic surge and pitch motion. Experimental results are available for these conditions and are used for baseline validation. The rotor is analyzed in both rated operating conditions and low wind speeds, where unsteady aerodynamic effects are expected to be more pronounced. Results show that BEM, despite its simplicity, can adequately model the aerodynamics of FOWTs in most conditions if augmented with a dynamic inflow model.
Original languageAmerican English
Pages (from-to)1069-1088
Number of pages20
JournalWind Energy Science Discussions
Issue number5
StatePublished - 2024

Bibliographical note

See NREL/JA-5000-87376 for article as published in Wind Energy Science Discussions

NREL Publication Number

  • NREL/JA-5000-90094


  • blade-element/momentum (BEM)
  • computational fluid dynamics (CFD)
  • dynamic wake
  • floating offshore wind turbine (FOWT)
  • unsteady aerodynamics
  • vortex wake


Dive into the research topics of 'Going Beyond BEM with BEM: An Insight into Dynamic Inflow Effects on Floating Wind Turbines'. Together they form a unique fingerprint.

Cite this