Screening of Available Tools for Dynamic Mooring Analysis of Wave Energy Converters

Thomsen, Jonas Bjerg; Ferri, Francesco; Kofoed, Jens Peter

doi:10.3390/en10070853

Cited by 15 publications

(10 citation statements)

References 11 publications

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“…Damage conditions, such as line breakage, may also be included. The degree of accuracy that linear-potential-flow-based models can reach when used to simulate extreme waves is a subject of recent studies ( [13,22,31]), and it is clearly expected to be larger in deep-water, where non-linearities are less important.…”

Section: Short Description Of the Numerical Modelmentioning

confidence: 99%

Effects of Mooring Compliancy on the Mooring Forces, Power Production, and Dynamics of a Floating Wave Activated Body Energy Converter

Martinelli

Zanuttigh

2018

Energies

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The paper aims at investigating the interactions between a floating wave energy device (WEC) and its mooring system under a variety of wave conditions (regular and irregular, perpendicular and oblique, ordinary and extreme). The analyzed WEC is the DEXA, a wave activated body point absorber, of the type that performs better when aligned to the incident wave direction. Two typologies of mooring systems were studied: for limited depths, the spread system, with a disposition of the lines that do not constrain the yaw movements; for large depths, the catenary anchor leg mooring (CALM) system. The spread system was experimentally investigated, including a realistic power take-off system, to capture non-linear behaviors and assess device motions, power production, and forces on mooring lines. The CALM system was numerically simulated, as mooring modelling is more reliable in deep waters and allows testing of a number of different configurations, by changing the number of the mooring lines and the mooring layout. The experiments showed that a reduction of the mooring compliancy increases the power production. The numerical simulations showed that a redundancy on the number of chains allows a better distribution of the loads, with advantages on reliability and costs.

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Section: Short Description Of the Numerical Modelmentioning

confidence: 99%

Effects of Mooring Compliancy on the Mooring Forces, Power Production, and Dynamics of a Floating Wave Activated Body Energy Converter

Martinelli

Zanuttigh

2018

Energies

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“…In case of floating bodies with a complex shape, the Boundary Element Method (BEM) is commonly implemented [17,18], obtaining steady solutions by solving numerically a boundary value problem in the frequency-domain. However, although these frequency-domain models are powerful and accurate in solving linear problems, they are usually implemented to provide hydrodynamic characteristics of floating devices and are coupled to time-domain simulations to analyze the response of moored structures [19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Implementation and Validation of a Potential Model for a Moored Floating Cylinder under Waves

Gaeta

Segurini

Moreno³

et al. 2020

JMSE

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A three degrees-of-freedom model based on the potential flow theory was implemented to represent the motion of a slender cylindrical buoy under waves. The model calibration was performed by means of the comparison between the model results and the experiments performed at the Laboratory of Hydraulic Engineering of the University of Bologna (Italy). The dynamics of the floating cylinder, placed at the mid-section of the wave flume and anchored at the bottom through a mooring system of four catenaries, were obtained through videography analysis, providing surge, heave and pitch motions. The implementation of the mathematical model consisted of two main parts: The first has been developed in the frequency domain by applying NEMOH to assess the hydrodynamic coefficients of the object, i.e., the excitation, radiation and added mass coefficients; then, the used mooring system was included in the time-domain model, solving the motion of the floating cylinder, by calibrating the mooring coefficients by comparing the results with the data. The simplicity of the implemented model is a very important feature, and it should be used as a preliminary study to understand the response of moored floating cylinders and others floating bodies under waves.

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“…In the last decade, a number of cable models have been explored, validated or coupled with the multi-body dynamics of floating offshore wind turbines and wave energy devices for numerical simulation, including the finite element model [8,9], the multi-body dynamics model [10], the lumped mass models [11,12] and the finite difference model [13][14][15][16][17]. A review of the available models and simulation tools of mooring cables can be found in [18,19]. Presently, mathematical modeling of mooring cables is still a topic area, e.g.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear periodic response analysis of mooring cables using harmonic balance method

Chen

Basu

Nielsen

2019

Journal of Sound and Vibration

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Mooring cables are critical components of ocean renewable energy systems including offshore floating wind turbines and wave energy converters. Mooring cable dynamics is strongly nonlinear resulting from the geometric effect, hydrodynamic loads and probably seabed interactions. Time-domain methods are commonly used for numerical simulation. This study formulates a nonlinear frequency domain multi-harmonic balance method for efficient analysis of a mooring cable subjected to periodic fairlead motions. The periodic responses are of particular interest to investigate the mooring effect on the platform. In the formulation, the governing equations of the three-dimensional cable motions are spatially discretized using the finite difference method; the nonlinear ordinary differential equations are subsequently transformed into frequency domain by expanding both the structural responses and the nonlinear nodal forces using truncated Fourier series, leading to a set of nonlinear algebraic equations of the Fourier coefficients. The equations are eventually solved using Newton's method where the alternating frequency/time domain method is used to handle the nonlinearity effect. The presented method is then compared to a time-domain method by numerical studies of a mooring cable. The results show that the method is of comparable accuracy as the time-domain method while it is generally more efficient. The proposed method shows promising results even when the cable tension becomes non-positive for a period of time during the cable motion, which is a known ill-posed problem for time-domain methods.

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Screening of Available Tools for Dynamic Mooring Analysis of Wave Energy Converters

Cited by 15 publications

References 11 publications

Effects of Mooring Compliancy on the Mooring Forces, Power Production, and Dynamics of a Floating Wave Activated Body Energy Converter

Effects of Mooring Compliancy on the Mooring Forces, Power Production, and Dynamics of a Floating Wave Activated Body Energy Converter

Implementation and Validation of a Potential Model for a Moored Floating Cylinder under Waves

Nonlinear periodic response analysis of mooring cables using harmonic balance method

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