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Going beyond BEM with BEM: an insight into dynamic inflow effects on floating wind turbines

Journal Article · · Wind Energy Science (Online)
 [1];  [2];  [2];  [1]
  1. Univ. degli Studi di Firenze (Italy)
  2. National Renewable Energy Laboratory (NREL), Golden, CO (United States)
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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.

Research Organization:
National Renewable Energy Laboratory (NREL), Golden, CO (United States)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Wind Energy Technologies Office
Grant/Contract Number:
AC36-08GO28308
OSTI ID:
2370508
Report Number(s):
NREL/JA--5000-90094; MainId:91872; UUID:eb4589e3-74d6-46a0-a5ce-19f10de62f6a; MainAdminId:72748
Journal Information:
Wind Energy Science (Online), Journal Name: Wind Energy Science (Online) Journal Issue: 5 Vol. 9; ISSN 2366-7451
Publisher:
Copernicus PublicationsCopyright Statement
Country of Publication:
United States
Language:
English

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Figures / Tables (16)

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Related Subjects

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