Numerical Study of Breaking Waves and Associated Wave Forces on a Jacket Substructure for Offshore Wind Turbines

Abstract The interest towards offshore wind energy has grown manifolds in the last few decades. Jacket structures are one of the most widely used substructures in the offshore wind turbine installations for intermediate water depths. Offshore structures are exposed to breaking waves. The interaction of breaking waves with the jackets is quite complicated due to the multiple vertical, horizontal and diagonal members. In the present study, a numerical investigation of the wave hydrodynamics and wave forces exerted by regular breaking waves on a jacket is performed. The open-source CFD code REEF3D is used for this purpose, which raises the possibility to model the breaking process physically. The conducted model-scale laboratory experiments have been performed in the past such that a direct comparison is presented.

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Characteristics of the Wave Slamming Forces on Jacket Structures Under Plunging Breaking Waves Based on Experimental Data

Volume 7B: Ocean Engineering ◽

10.1115/omae2017-61789 ◽

2017 ◽

Cited By ~ 1

Author(s):

Jithin Jose ◽

Olga Podrażka ◽

Ove Tobias Gudmestad ◽

Witold Cieślikiewicz

Keyword(s):

Energy Demand ◽

Clean Energy ◽

Breaking Waves ◽

Offshore Structures ◽

Offshore Wind ◽

Wave Forces ◽

Breaking Wave ◽

Jacket Structures ◽

Wave Slamming ◽

Wave Properties

Due to increased energy demand and thrive for clean energy, offshore wind energy has become popular these days. A large number of offshore wind turbines supported by fixed type substructures have been installed, among which jacket structures are getting popular in recent times. The forces from breaking waves are a major concern in the design of offshore structures installed in shallow waters. However, there are only limited studies available regarding breaking wave forces on jacket structures and still there exist many uncertainties in this area. During the WaveSlam experiment carried out in 2013, a jacket structure of 1:8 scale was tested on a large number of breaking wave conditions. Wave properties and the forces on the structure were measured during the experiment. The total wave slamming forces are being filtered from the experimental measured force using the Empirical Mode Decomposition method and local slamming forces are obtained by the Frequency Response Function method. Based on these results, the peak slamming force and slamming coefficients on the jacket members are estimated. The wave parameters (wave height and period) and wave front asymmetry are obtained from measured wave properties. The variation of slamming forces and slamming coefficients with respect to these parameters are also investigated.

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Maintenance Planning of Offshore Wind Turbine Using Condition Monitoring Information

Volume 4: Ocean Engineering; Ocean Renewable Energy; Ocean Space Utilization, Parts A and B ◽

10.1115/omae2009-79159 ◽

2009 ◽

Author(s):

Jose´ G. Rangel-Rami´rez ◽

John D. So̸rensen

Keyword(s):

Condition Monitoring ◽

Wind Turbines ◽

Wind Farm ◽

Offshore Structures ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Maintenance Planning ◽

Offshore Wind Turbines ◽

Inspection And Maintenance ◽

Monitoring Information

Deterioration processes such as fatigue and corrosion are typically affecting offshore structures. To “control” this deterioration, inspection and maintenance activities are developed. Probabilistic methodologies represent an important tool to identify the suitable strategy to inspect and control the deterioration in structures such as offshore wind turbines (OWT). Besides these methods, the integration of condition monitoring information (CMI) can optimize the mitigation activities as an updating tool. In this paper, a framework for risk-based inspection and maintenance planning (RBI) is applied for OWT incorporating CMI, addressing this analysis to fatigue prone details in welded steel joints at jacket or tripod steel support structures for offshore wind turbines. The increase of turbulence in wind farms is taken into account by using a code-based turbulence model. Further, additional modes t integrate CMI in the RBI approach for optimal planning of inspection and maintenance. As part of the results, the life cycle reliabilities and inspection times are calculated, showing that earlier inspections are needed at in-wind farm sites. This is expected due to the wake turbulence increasing the wind load. With the integration of CMI by means Bayesian inference, a slightly change of first inspection times are coming up, influenced by the reduction of the uncertainty and harsher or milder external agents.

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Detailed Study on Breaking Wave Interactions With a Jacket Structure Based on Experimental Investigations

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.4037829 ◽

2017 ◽

Vol 140 (2) ◽

Author(s):

Jithin Jose ◽

Olga Podrażka ◽

Ove Tobias Gudmestad ◽

Witold Cieślikiewicz

Keyword(s):

Wind Turbines ◽

Wave Breaking ◽

Offshore Structures ◽

Offshore Wind ◽

Wave Forces ◽

Breaking Wave ◽

Offshore Wind Turbines ◽

Wave Parameters ◽

Wave Slamming ◽

Breaking Wave Forces

Wave breaking is one of the major concerns for offshore structures installed in shallow waters. Impulsive breaking wave forces sometimes govern the design of such structures, particularly in areas with a sloping sea bottom. Most of the existing offshore wind turbines were installed in shallow water regions. Among fixed-type support structures for offshore wind turbines, jacket structures have become popular in recent times as the water depth for fixed offshore wind structures increases. However, there are many uncertainties in estimating breaking wave forces on a jacket structure, as only a limited number of past studies have estimated these forces. Present study is based on the WaveSlam experiment carried out in 2013, in which a jacket structure of 1:8 scale was tested for several breaking wave conditions. The total and local wave slamming forces are obtained from the experimental measured forces, using two different filtering methods. The total wave slamming forces are filtered from the measured forces using the empirical mode decomposition (EMD) method, and local slamming forces are obtained by the frequency response function (FRF) method. From these results, the peak slamming forces and slamming coefficients on the jacket members are estimated. The breaking wave forces are found to be dependent on various breaking wave parameters such as breaking wave height, wave period, wave front asymmetry, and wave-breaking positions. These wave parameters are estimated from the wave gauge measurements taken during the experiment. The dependency of the wave slamming forces on these estimated wave parameters is also investigated.

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Experimental Study on the Wave Loads on Monopile and Jacket Type Support of Offshore Wind Turbines

Volume 11A: Honoring Symposium for Professor Carlos Guedes Soares on Marine Technology and Ocean Engineering ◽

10.1115/omae2018-77715 ◽

2018 ◽

Author(s):

Jing Zhang ◽

Qin Liu ◽

Xing Hua Shi ◽

C. Guedes Soares

Keyword(s):

Experimental Study ◽

Wind Turbine ◽

Nonlinear Wave ◽

Wave Force ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Wave Forces ◽

Wave Loads ◽

Morison Equation ◽

Offshore Wind Turbines

As the offshore fixed wind turbine developed, more ones will be installed in the sea field with the depth 15–50 meters. Wave force will be one of the main forces that dominate the design of the wind turbine base, which is calculated using the Morison equation traditionally. This method can predict the wave forces for the small cylinders if the drag and inertia coefficients are obtained accurately. This paper will give a series scaled tests of monopile and jacket type base of the offshore wind turbine in tank to study the nonlinear wave loads.

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Numerical Study of a Proposed Semi-Submersible Floating Platform with Different Numbers of Offset Columns Based on the DeepCwind Prototype for Improving the Wave-Resistance Ability

Applied Sciences ◽

10.3390/app9061255 ◽

2019 ◽

Vol 9 (6) ◽

pp. 1255

Author(s):

Zhenqing Liu ◽

Yicheng Fan ◽

Wei Wang ◽

Guowei Qian

Keyword(s):

Wind Turbines ◽

Numerical Study ◽

Wind Farms ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Floating Platform ◽

Offshore Wind Turbines ◽

Irregular Wave ◽

Decay Test ◽

Floating Offshore Wind Turbines

DeepCwind semi-submersible floating offshore wind turbines have been widely examined, and in some countries this type of floating offshore wind turbine has been adopted in the construction of floating wind farms. However, the DeepCwind semi-submersible floating offshore wind turbines still experience large surge motion that limits their operational time. Therefore, in this study, a semi-submersible floating platform with different numbers of offset columns, but with the same total weight, based on the DeepCwind prototype is proposed. From the free-decay test, it was found that the number of the floating columns will affect the natural frequency of the platform. Furthermore, the regular wave test in the time domain and the irregular wave test in the frequency domain show that increasing the number of the floating columns will reduce the surge motion greatly, while the effects in the heave and pitch motions are not obvious.

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Modeling Breaking Waves for Fixed-Bottom Support Structures for Offshore Wind Turbines

ASME 2018 1st International Offshore Wind Technical Conference ◽

10.1115/iowtc2018-1095 ◽

2018 ◽

Author(s):

Hannah M. Johlas ◽

Spencer Hallowell ◽

Shengbai Xie ◽

Pedro Lomonaco ◽

Matthew A. Lackner ◽

...

Keyword(s):

Wind Turbines ◽

Water Depth ◽

Adaptive Mesh Refinement ◽

Adaptive Mesh ◽

Breaking Waves ◽

Offshore Wind ◽

Breaking Wave ◽

Intermediate Water ◽

Offshore Wind Turbines ◽

Ocean Conditions

Fixed-bottom offshore wind turbines (OWTs) are typically located in shallow to intermediate water depth, where waves are likely to break. Support structure designs for such turbines must account for loads due to breaking waves, but predictions from breaking wave models often disagree with each other and with observed behavior. This variability indicates the need for a better understanding of each model’s strengths and limitations, especially for different ocean conditions. This work evaluates and improves the accuracy of common breaking wave criteria through comparison to Computational Fluid Dynamics (CFD) simulations of breaking waves. The simulated ocean conditions are representative of potential U.S. East Coast offshore wind energy development sites, but the discussion of model accuracy and limitations can be applied to any location with similar ocean conditions. The waves are simulated using CONVERGE, a commercial CFD software that uses a Volume of Fluid (VOF) approach and includes adaptive mesh refinement at the evolving air-water interface. First, the CFD model is validated against experimental data for shoaling and breaking wave surface elevations. Second, 2D simulations of breaking waves are compared to widely-used breaking wave limits (McCowan, Miche, and Goda) for different combinations of wave height, wavelength, water depth, and seafloor slope. Based on these comparisons, the accuracy and limitations of each breaking limit model are discussed. General usage guidelines are then recommended.

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Numerical and Experimental Investigation of the Wave Loading on a Three-Legged Offshore Wind Turbine Jacket Platform

Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics ◽

10.1115/omae2018-78416 ◽

2018 ◽

Cited By ~ 1

Author(s):

Ioannis K. Chatjigeorgiou ◽

Konstantinos Chatziioannou ◽

Vanessa Katsardi ◽

Apostolos Koukouselis ◽

Euripidis Mistakidis

Keyword(s):

Wave Structure ◽

Element Model ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Wave Forces ◽

Intermediate Water ◽

Wave Loads ◽

Wave Loading ◽

Scaled Model ◽

The Time Domain

The purpose of this work is to examine a three-legged jacket tower support system subjected to wave loading. To this end, linear as well as nonlinear wave scenarios are investigated. The structure was designed for offshore wind turbines installed in intermediate water depths. The phenomenon of the wave-structure interaction is examined experimentally with a 1:18 scaled model as well as numerically with the use of Finite Element Model (FEM). The structural calculations were performed using the structural analysis software SAP2000, which was enhanced by a special programming interface that was developed to calculate the wave loading and to directly apply the wave loads on the structural members. The FEM model in combination with the key parameters that are taken into account, provides a good correlation with the experimental results. The wave theories of Airy and Stokes 5th are employed for the calculation of the wave particle kinematics. The resulting wave forces are examined both in the frequency and in the time domain.

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The advanced p-y method for analyzing the behaviour of large-diameter monopiles supporting offshore wind turbines

E3S Web of Conferences ◽

10.1051/e3sconf/202020512008 ◽

2020 ◽

Vol 205 ◽

pp. 12008

Author(s):

William F Van Impe ◽

Shin-Tower Wang

Keyword(s):

Wind Turbine ◽

Large Diameter ◽

Offshore Structures ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Response Curves ◽

Current Design ◽

Jacket Structures ◽

Load Tests ◽

Offshore Industry

The analyses of monopile foundations have been heavily based on the p-y response curves (to represent lateral soil resistances) published by API RP 2GEO (2011) and DNV (2013), which are proven reliable and applicable for piles with smaller diameters that were normally used for jacket structures in the offshore industry. However, concerns have been raised about the validity of semi-empirical p-y criteria for large-diameter piles. Wind turbine monopiles have a significantly larger diameter and smaller length to diameter ratio than typical piles used for offshore structures. The ratio of the length to the diameter for a monopile typically is also significantly smaller than those used in the API load tests. Therefore, the response of a monopile may be more like a rigid rotation, with components of resistance mobilized at the tip and axially along the sides as it rotates. This behaviour is in contrast to long slender piles that respond to lateral loading in bending rather than rotation. The objective of this paper is to analyze the factors that may contribute to the apparent conservatism in the current design practice for large-diameter monopile foundations and to provide improved solutions on how to analyze and design the large-diameter monopiles for offshore wind turbine using the p-y method.

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Experimental Investigations of Breaking Wave Impact Forces on a Monopile Substructure for Offshore Wind Turbines Under Regular Breaking Waves

Volume 4A: Dynamics, Vibration, and Control ◽

10.1115/imece2017-71227 ◽

2017 ◽

Author(s):

Vipin Chakkurunni Palliyalil ◽

Panneer Selvam Rajamanickam ◽

Mayilvahanan Alagan Chella ◽

Vijaya Kumar Govindasamy

Keyword(s):

Circular Cylinder ◽

Wind Turbines ◽

Breaking Waves ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Breaking Wave ◽

Wave Impact ◽

Offshore Wind Turbines ◽

Impact Forces ◽

The Impact

The main objective of the paper is to investigate wave impact forces from breaking waves on a monopile substructure for offshore wind turbine in shallow waters. This study examines the load assessment parameters relevant for breaking wave forces on a vertical circular cylinder subjected to breaking waves. Experiments are conducted in a shallow water flume and the wave generation is based on piston type wave maker. The experiments are performed with a vertical circular cylinder with diameter, D = 0.20m which represents a monopile substructure for offshore wind turbines with regular waves of frequencies around 0.8Hz. The experimental setup consists of a 1/10 slope followed by a horizontal bed portion with a water depth of 0.8m. Plunging breaking waves are generated and free surface elevations are measured at different locations along the wave tank from wave paddle to the cylinder in order to find the breaking characteristics. Wave impact pressures are measured on the cylinder at eight different vertical positions along the height of the cylinder under breaking waves for different environmental conditions. The wave impact pressures and wave surface elevations in the vicinity of the cylinder during the impact for three different wave conditions are presented and discussed.

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