Prediction of long-term fatigue damage of a hydraulic cylinder of a wave energy converter subjected to internal fluid pressure induced by wave loads

2013 ◽  
Vol 2 ◽  
pp. 43-60 ◽  
Author(s):  
Limin Yang ◽  
Torgeir Moan
Keyword(s):  
Fatigue Damage ◽  
Wave Energy ◽  
Fluid Pressure ◽  
Hydraulic Cylinder ◽  
Wave Energy Converter ◽  
Wave Loads ◽  
Energy Converter ◽  
Internal Fluid

Fatigue Analysis of a Point Absorber Wave Energy Converter Subjected to Passive and Reactive Control

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
A. S. Zurkinden ◽  
S. H. Lambertsen ◽  
L. Damkilde ◽  
Z. Gao ◽  
T. Moan
Keyword(s):  
Fatigue Damage ◽  
Wave Energy ◽  
Stress Responses ◽  
Fatigue Analysis ◽  
Wave Energy Converter ◽  
Wave Loads ◽  
Reactive Control ◽  
Energy Converter ◽  
Set Up ◽  
Frequency Domain Approach

This paper investigates the effect of a passive and reactive control mechanism on the accumulated fatigue damage of a wave energy converter (WEC). Interest is focused on four structural details of the Wavestar arm, which is used as a case study here. The fatigue model is set up as an independent and generic toolbox, which can be applied to any other global response model of a WEC device combined with a control system. The stress responses due to the stochastic wave loads are computed by a finite element method (FEM) model using the frequency-domain approach. The fatigue damage is calculated based on the spectral-based fatigue analysis in which the fatigue is described by the given spectral moments of the stress response. The question will be discussed, which control case is more favorable regarding the tradeoff between fatigue damage reduction and increased power production.

Long-Term Stochastic Dynamic Analysis of a Combined Floating Spar-Type Wind Turbine and Wave Energy Converter (STC) System for Mooring Fatigue Damage and Power Prediction

2014 ◽  
Author(s):  
Nianxin Ren ◽  
Zhen Gao ◽  
Torgeir Moan
Keyword(s):  
Wind Turbine ◽  
Fatigue Damage ◽  
Wave Energy ◽  
Wind Wave ◽  
Wave Energy Converter ◽  
Force Model ◽  
Stochastic Dynamic ◽  
Energy Converter ◽  
Short Term

In this work, a combined concept called Spar-Toru-Combination (STC) involving a spar-type floating wind turbine (FWT) and an axi-symmetric two-body wave energy converter (WEC) is considered. From the views of both long-term fatigue damage prediction of the mooring lines and the annual energy production estimation, a coupled analysis of wind-wave induced long-term stochastic responses has been performed using the SIMO-TDHMILL code in the time domain, which includes 79200 one-hour short term cases (the combination of 22 selected mean wind speeds * 15 selected significant wave heights * 12 selected spectral peak wave periods * 20 random seeds). The hydrodynamic loads on the Spar and Torus are estimated using potential theory, while the aerodynamic loads on the wind rotor are calculated by the validated simplified thrust force model in the TDHMILL code. Considering the long-term wind-wave joint distribution in the northern North Sea, the annual fatigue damage of the mooring line for the STC system is obtained by using the S-N curve approach and Palmgren-Miner’s linear damage hypothesis. In addition, the annual wind and wave power productions are also obtained by using hourly mean output power for each short-term condition and the joint wind-wave distribution.

Loads and Dynamic Response of a Floating Wave Energy Converter due to Regular Waves From CFD Simulations

2016 ◽  
Author(s):  
Anna Büchner ◽  
Thomas Knapp ◽  
Martin Bednarz ◽  
Philipp Sinn ◽  
Arndt Hildebrandt
Keyword(s):  
Dynamic Response ◽  
Boundary Conditions ◽  
Wave Energy ◽  
Single Point ◽  
Breaking Waves ◽  
Wave Energy Converter ◽  
Wave Loads ◽  
Regular Waves ◽  
Energy Converter ◽  
Set Up

The commercial CFD code ANSYS Fluent is used for the three-dimensional estimation of wave loads and the dynamic response of a floating single point wave energy converter of the SINN Power wave power plant due to non-breaking and unidirectional waves in coastal waters. The VoF method is used to model the free surface and wave theories to set up the boundary conditions at the inlet for regular waves. The wave induced vertical motions of the floating module are computed by a sixDoF solver. Preliminary 2D and 3D studies to set up boundary conditions, mesh densities and solver settings were performed. The numerical results were compared to analytical solutions in form of water surface elevations and wave kinematics which showed good agreement. The paper presents the dynamic response of the floating module for different load cases in terms of non-breaking waves. The resulting horizontal and vertical forces at the floating module will be presented and explained by the flow dynamics. Time and space depending velocities and pressure distributions including details on vortex separation will be given, which reveal valuable insights on the contribution of inertia and drag forces leading to the dynamic structural response of the floating devices.

Performance Characteristics of a Tightly Moored Piston-Like Wave Energy Converter Under First- and Second-Order Wave Loads

2008 ◽  
Author(s):  
Spyros A. Mavrakos ◽  
George M. Katsaounis ◽  
Ioannis K. Chatjigeorgiou
Keyword(s):  
Wave Energy ◽  
Second Order ◽  
Wave Energy Converter ◽  
Performance Characteristics ◽  
Hydrodynamic Characteristics ◽  
Diffraction Radiation ◽  
Wave Loads ◽  
Energy Converter ◽  
Eigenfunction Expansions ◽  
First Order

The paper deals with the presentation of a model to predict performance characteristics of a tightly moored piston-like wave energy converter which is allowed to move in heave, pitch and sway modes of motion. The WEC’s piston-like arrangement consists of two floating concentric cylinders, the geometry of which allow the existence of a cylindrical moonpool between the external cylinder, the ‘torus’ and the inner cylinder, the ‘piston’. The first-order hydrodynamic characteristics of the floating device, i.e. exciting wave forces and hydrodynamic parameters, are evaluated using a linearized diffraction-radiation semi-analytical method of analysis that is suited for the type of bodies under consideration. According to the analysis method used, matched axisymmetric eigenfunction expansions of the velocity potentials in properly defined fluid regions around the body are introduced to solve the respective diffraction and radiation problems and to calculate the floats’ hydrodynamic characteristics in the frequency domain (Mavrakos et al. 2004, 2005). Based on these characteristics, the retardation forcing terms are calculated, which account for the memory effects of the motion. In this procedure, the coupling terms between the different modes of motion are properly formulated and taken into account (Cummins, 1962; Faltinsen, 1990). The floating WEC is connected to an underwater hydraulic cylinder that feeds a hydraulic system with pressurized oil. The performance of the system under the combined excitation of both first- and second order wave loads is here analyzed. To this end, the diffraction forces originated from the second order wave potentials are computed using a semi-analytical formulation which, by extension of the associated first-order solution, is based on matched axisymmetric eigenfunction expansions.

Evaluation of long-term power capture performance of a bistable point absorber wave energy converter in South China Sea

2021 ◽  
Vol 237 ◽  
pp. 109338
Author(s):  
Nianfan Zhang ◽  
Xiantao Zhang ◽  
Longfei Xiao ◽  
Handi Wei ◽  
Weixing Chen
Keyword(s):  
South China Sea ◽  
South China ◽  
Wave Energy ◽  
Wave Energy Converter ◽  
Energy Converter ◽  
China Sea ◽  
Point Absorber ◽  
Power Capture

scholarly journals Full long-term design response analysis of a wave energy converter

2018 ◽  
Vol 116 ◽  
pp. 356-366 ◽  
Author(s):  
Ryan G. Coe ◽  
Carlos Michelen ◽  
Aubrey Eckert-Gallup ◽  
Cédric Sallaberry
Keyword(s):  
Wave Energy ◽  
Wave Energy Converter ◽  
Response Analysis ◽  
Energy Converter

Structural Modeling and Analysis of a Wave Energy Converter Applying Dynamical Substructuring Method

2013 ◽  
Author(s):  
Andrew S. Zurkinden ◽  
Lars Damkilde ◽  
Zhen Gao ◽  
Torgeir Moan
Keyword(s):  
Wave Energy ◽  
Structural Modeling ◽  
Wave Energy Converter ◽  
Computational Time ◽  
Response Analysis ◽  
Fe Model ◽  
Wave Loads ◽  
Energy Converter ◽  
Modeling And Analysis ◽  
Survival Mode

This paper deals with structural modeling and analysis of a wave energy converter. The device, called Wavestar, is a bottom fixed structure, located in a shallow water environment at the Danish Northwest coast. The analysis is concentrated on a single float and its structural arm which connects the WEC to a jackup structure. The wave energy converter is characterized by having an operational and survival mode. The survival mode drastically reduces the exposure to waves and therfore to the wave loads. Structural response analysis of the Wavestar arm is carried out in this study. Due to the relative stiff behavior of the arm the calculation can be reduced to a quasi-static analysis. The hydrodynamic and the structural analyses are thus performed separately. In order to reduce the computational time of the finite element calculation the main structure is modeled as a superelement. The structural detail, where the stress analysis is carried out, is connected with the superstructure by interface nodes. The analysis is conducted for two different control situations. Numerical results will be presented which can be further used to carry out fatigue analysis in which a more refined FE model is required to obtain the stress concentration factors.

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