The Influence of Sea Waves on Offshore Wind Turbine Aerodynamics

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
A. AlSam ◽  
R. Szasz ◽  
J. Revstedt
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Offshore Wind ◽  
Speed Ratio ◽  
Offshore Wind Turbine ◽  
Intensity Level ◽  
Sea Waves ◽  
Power Extraction ◽  
Wind Turbine Aerodynamics ◽  
Large Eddy

The impacts of swells on the atmospheric boundary layer (ABL) flows and by this on the standalone offshore wind turbine (WT) performance are investigated by using large eddy simulations (LES) and actuator-line techniques. At high swell to wind speed ratio, the swell-induced stress reduces the total wind stress resulting in higher wind velocity, less wind shear, and lower turbulence intensity level. These effects increase by increasing swell to wind speed ratio (C/U) and/or swell steepness. Moreover, for the same hub-height wind speed (Uhub), the presence of swells increases the turbine power extraction rate by about 3% and 8.4% for C/Uhub = 1.53 and 2.17, respectively.

scholarly journals Numerical Validation of Floating Offshore Wind Turbine Scaled Rotors for Surge Motion

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2578 ◽  
Author(s):  
Krishnamoorthi Sivalingam ◽  
Steven Martin ◽  
Abdulqadir Singapore Wala
Keyword(s):  
Wind Turbine ◽  
Turbine Rotor ◽  
Power Converter ◽  
Experimental Results ◽  
Offshore Wind ◽  
Speed Ratio ◽  
Offshore Wind Turbine ◽  
Floating Offshore Wind Turbine ◽  
Aerodynamic Loads ◽  
Unsteady Aerodynamic

Aerodynamic performance of a floating offshore wind turbine (FOWT) is significantly influenced by platform surging motions. Accurate prediction of the unsteady aerodynamic loads is imperative for determining the fatigue life, ultimate loads on key components such as FOWT rotor blades, gearbox and power converter. The current study examines the predictions of numerical codes by comparing with unsteady experimental results of a scaled floating wind turbine rotor. The influence of platform surge amplitude together with the tip speed ratio on the unsteady aerodynamic loading has been simulated through unsteady CFD. It is shown that the unsteady aerodynamic loads of FOWT are highly sensitive to the changes in frequency and amplitude of the platform motion. Also, the surging motion significantly influences the windmill operating state due to strong flow interaction between the rotating blades and generated blade-tip vortices. Almost in all frequencies and amplitudes, CFD, LR-BEM and LR-uBEM predictions of mean thrust shows a good correlation with experimental results.

scholarly journals Large eddy simulations of offshore wind turbine wakes for two floating platform types

2020 ◽  
Vol 1452 ◽  
pp. 012034
Author(s):  
H M Johlas ◽  
L A Martínez-Tossas ◽  
M A Lackner ◽  
D P Schmidt ◽  
M J Churchfield
Keyword(s):  
Wind Turbine ◽  
Large Eddy Simulations ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Floating Platform ◽  
Large Eddy

Numerical Simulations of Aerodynamic Feature for Variable Speed Offshore Wind Turbine

2011 ◽  
Vol 52-54 ◽  
pp. 1556-1559
Author(s):  
Ping He ◽  
Nai Chao Chen ◽  
Dan Mei Hu
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Gas Flow ◽  
Rapid Change ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Total Force ◽  
Variable Speed ◽  
Horizontal Axis Wind Turbine ◽  
Blade Height

The liquid-gas flow is proposed to accurately simulate the offshore environmental state. The aerodynamic feature is estimated using the three-dimensional model of horizontal-axis wind turbine with NRELS809 series aerofoil by means of the simulating software tool of FLUENT. The variable speed is implemented via the six different wind speeds. The calculated results show that the similarly evolutional tendency of velocity occurs in the wake region when operating at the six variable speeds. The stall speed is related to blade height and wind speed. The small blade height or large wind speed also leads to the serious stall phenomenon. The total force is conducted to estimate the potential capability for leeward and windward surface to capture wind power. The calculated results reveal that the larger wind speed facilitates generating the more magnitude of total force. However, the velocity and force feature for the wind turbine has the especially rapid change at the wind speed of 6 m/s, which perhaps results from the intrinsic geometry and configuration.

scholarly journals Validation of Numerical Models of the Offshore Wind Turbine From the Alpha Ventus Wind Farm Against Full-Scale Measurements Within OC5 Phase III

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Wojciech Popko ◽  
Amy Robertson ◽  
Jason Jonkman ◽  
Fabian Wendt ◽  
Philipp Thomas ◽  
...  
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Wind Farm ◽  
Operating Conditions ◽  
Offshore Wind ◽  
Phase Iii ◽  
Offshore Wind Turbine ◽  
Discrete Fourier Transforms ◽  
Simulation Tools ◽  
Axial Forces

Abstract The main objective of the Offshore Code Comparison Collaboration Continuation, with Correlation (OC5) project is validation of aero-hydro-servo-elastic simulation tools for offshore wind turbines (OWTs) through comparison of simulated results to the response data of physical systems. Phase III of the OC5 project validates OWT models against the measurements recorded on a Senvion 5M wind turbine supported by the OWEC Quattropod from the alpha ventus offshore wind farm. The following operating conditions of the wind turbine were chosen for the validation: (1) idling below the cut-in wind speed, (2) rotor-nacelle assembly (RNA) rotation maneuver below the cut-in wind speed, (3) power production below and above the rated wind speed, and (4) shutdown. A number of validation load cases were defined based on these operating conditions. The following measurements were used for validation: (1) strains and accelerations recorded on the support structure and (2) pitch, yaw, and azimuth angles, generator speed, and electrical power recorded from the RNA. Strains were not directly available from the majority of the OWT simulation tools; therefore, strains were calculated based on out-of-plane bending moments, axial forces, and cross-sectional properties of the structural members. The simulation results and measurements were compared in terms of time series, discrete Fourier transforms, power spectral densities, and probability density functions of strains and accelerometers. A good match was achieved between the measurements and models setup by OC5 Phase III participants.

Modelling the Aerodynamics of a Floating Wind Turbine Model Using a CFD-Based Actuator Disc Method

2019 ◽  
Author(s):  
Ryan Bezzina ◽  
Tonio Sant ◽  
Daniel Micallef
Keyword(s):  
Wind Turbine ◽  
Offshore Wind ◽  
Speed Ratio ◽  
Offshore Wind Turbine ◽  
Floating Platform ◽  
Blade Element Theory ◽  
Floating Wind Turbine ◽  
Actuator Disc ◽  
Turbine Wake ◽  
Blade Element

Abstract Significant research in the field of Floating Offshore Wind Turbine (FOWT) rotor aerodynamics has been documented in literature, including validated aerodynamic models based on Blade Element Momentum (BEM) and vortex methods, amongst others. However, the effects of platform induced motions on the turbine wake development downstream of the rotor plane or any research related to such areas is rather limited. The aims of this paper are two-fold. Initially, results from a CFD-based Actuator Disc (AD) code for a fixed (non-surging) rotor are compared with those obtained from a Blade Element Momentum (BEM) theory, as well as previously conducted experimental work. Furthermore, the paper also emphasises the effect of tip speed ratio (TSR) on the rotor efficiency. This is followed by the analysis of floating wind turbines specifically in relation to surge displacement, through an AD technique implemented in CFD software, ANSYS Fluent®. The approach couples the Blade Element Theory (BET) for estimating rotating blade loads with a Navier Stokes solver to simulate the turbine wake. With regards to the floating wind turbine cases, the code was slightly altered such that BET was done in a transient manner i.e. following sinusoidal behaviour of waves. The AD simulations were performed for several conditions of TSRs and surge frequencies, at a constant amplitude. Similar to the fixed rotor analysis, significant parameters including thrust and power coefficients, amongst others, were studied against time and surge position. The floating platform data extracted from the AD approach was compared to the non-surging turbine data obtained, to display platform motion effects clearly. Data from hot wire near wake measurements and other simulation methods were also consulted.

scholarly journals Numerical Analysis and Parameter Optimization of J-Shaped Blade on Offshore Vertical Axis Wind Turbine

Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6426
Author(s):  
Lin Pan ◽  
Ze Zhu ◽  
Haodong Xiao ◽  
Leichong Wang
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Vertical Axis ◽  
Offshore Wind ◽  
Speed Ratio ◽  
Offshore Wind Turbine ◽  
Offshore Wind Turbines ◽  
Tip Speed Ratio ◽  
Turbulence Effect ◽  
Dimensional Simulation

In this study, the performance of offshore wind turbines at low tip speed ratio (TSR) is studied using computational fluid dynamics (CFD), and the performance of offshore wind turbines at low tip speed ratio (TSR) is improved by revising the blade structure. First, the parameters of vertical axis offshore wind turbine are designed based on the compactness iteration, a CFD simulation model is established, and the turbulence model is selected through simulation analysis to verify the independence of grid and time step. Compared with previous experimental results, it is shown that the two-dimensional simulation only considers the plane turbulence effect, and the simulation turbulence effect performs more obviously at a high tip ratio, while the three-dimensional simulation turbulence effect has well-fitting performance at high tip ratio. Second, a J-shaped blade with optimized lower surface is proposed. The study showed that the optimized J-shaped blade significantly improved its upwind torque and wind energy capture rate. Finally, the performance of the optimized J-blade offshore wind turbine is analyzed.

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