Time-Varying Wave and Current-Induced Scour Around Offshore Wind Turbines

2007 ◽  
Author(s):  
A. W. Nielsen ◽  
E. A. Hansen
Keyword(s):  
Material Properties ◽  
Time Development ◽  
Offshore Wind ◽  
Scour Depth ◽  
Time Varying ◽  
Engineering Model ◽  
Offshore Wind Turbines ◽  
Industry Standard ◽  
Pile Diameter ◽  
Physical Experiments

The paper presents the engineering model, WiTuS (Wind Turbine Scour), which uses the results of several previous published physical experiments with scour around cylinders to determine the time development of the scour hole around the pile due to the actual and the previous wave and current climate. The WiTuS includes: • Time-varying water level, sea states and current. • Seabed material properties. • Description of the scour geometry around the pile. Simulations presented in the paper show that for typical North Sea conditions the scour depth will be around 0.3 times the pile diameter in periods with larger waves, which is a significant reduction from 1.3 times the pile diameter which is often seen as the industry standard.

Effects of Sand-Clay Mixtures on Scour Around Vertical Piles Due to Long-Crested and Short-Crested Nonlinear Random Waves

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Dag Myrhaug ◽  
Muk Chen Ong
Keyword(s):  
Coastal Ocean ◽  
Stochastic Method ◽  
Offshore Wind ◽  
Pile Foundations ◽  
Scour Depth ◽  
Regular Wave ◽  
Random Waves ◽  
Offshore Wind Turbines ◽  
Equilibrium Scour Depth ◽  
Nonlinear Random Waves

This note provides a practical stochastic method by which the effects of sand-clay mixtures on the maximum equilibrium scour depth around vertical piles exposed to long-crested (2D) and short-crested (3D) nonlinear random waves can be derived. This is made by using the regular wave formulas for scour depth for sand-clay mixtures by Dey et al. (2011, Scour at Vertical Piles in Sand-Clay Mixtures Under Waves,” J. Waterway, Port, Coastal, Ocean Eng., 137(6), pp. 324–331) and the stochastic method presented by Myrhaug and Ong (2013, “Scour Around Vertical Pile Foundations for Offshore Wind Turbines Due to Long-Crested and Short-Crested Nonlinear Random Waves,” ASME J. Offshore Mech. Arctic Eng., 135(1), p. 011103). Thus the present results are supplementary to those presented in the latter reference. An example calculation is provided.

scholarly journals EVOLUTION OF LOCAL SCOUR AROUND A COLLARED MONOPILE THROUGH TIDAL CYCLES

2012 ◽  
Vol 1 (33) ◽  
pp. 113 ◽  
Author(s):  
David J McGovern ◽  
Suzana Ilic ◽  
Andrew M Folkard ◽  
Stuart J McLelland ◽  
Brendan J Murphy
Keyword(s):  
Time Development ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Scour Depth ◽  
Half Cycle ◽  
Simplified Approach ◽  
Unidirectional Flow ◽  
Tidal Cycles ◽  
Equilibrium Scour Depth ◽  
Scour Protection

This paper presents the results of an experiment designed to assess the time-development of scour around an offshore wind turbine collared monopile over a number of tidal cycles. One collar shape and location was investigated. The scour developed more slowly and the scour depth was shallower than for the case of a smooth monopile throughout the majority of the first half-cycle. This difference reduced quite rapidly during the second half-cycle and the scour depth at the end of two tidal cycles was essentially the same as for the smooth monopile. The time development of the scour was compared with results from existing empirical models for the time-development of scour under unidirectional flow. As expected, these models give a much smoother evolution of scour and different scour rates than those measured. Time variation in scour depth was better reproduced with a simplified approach for prediction of the time-varying development of scour. This also highlighted a problem with estimation of the time scale for the development of the equilibrium scour depth. Further investigations are needed before this alternative scour protection is completely rejected.

Scour Around Vertical Pile Foundations for Offshore Wind Turbines due to Long-Crested and Short-Crested Nonlinear Random Waves

2011 ◽  
Author(s):  
Dag Myrhaug ◽  
Muk Chen Ong
Keyword(s):  
Offshore Wind ◽  
Wave Crest ◽  
Random Wave ◽  
Scour Depth ◽  
Height Distribution ◽  
Random Waves ◽  
Offshore Wind Turbines ◽  
Nonlinear Random Waves ◽  
Wave Induced ◽  
2D And 3D

This paper provides a practical stochastic method by which the maximum scour depth around vertical piles exposed to long-crested (2D) and short-crested (3D) nonlinear random waves can be derived. The approach is based on assuming the waves to be a stationary narrow-band random process, adopting the Forristall (2000) wave crest height distribution representing both 2D and 3D nonlinear random waves, and using the regular wave formulas for scour depth by Sumer et al. (1992b). An example of calculation is provided. Tentative approaches to related random wave-induced scour cases are also suggested.

Corrosion Protection Design of Support Structures for Offshore Wind Turbines with Analysis of Material Properties

2013 ◽  
Vol 703 ◽  
pp. 336-339
Author(s):  
Bi Xiang Mei
Keyword(s):  
Corrosion Protection ◽  
Wind Turbines ◽  
Cathodic Protection ◽  
Material Properties ◽  
Offshore Wind ◽  
Support Structures ◽  
Marine Corrosion ◽  
Offshore Wind Turbines ◽  
Current State

The paper provides a review about the corrosion ,corrosion protection and material properties of support structures for offshore wind turbines. Firstly, the current state of corrosion protection research on offshore wind turbines is discussed. Secondly, types of the marine corrosion environment, corrosivity categories and material properties are summarized in a systematic way.Finally, practical solutions to the corrosion protection of support structures, including cathodic protection ,coatings and silane impregnation, are discussed.

Pitch Angle Control of Floating Offshore Wind Turbines by H∞ Control

2014 ◽  
Vol 134 (8) ◽  
pp. 1096-1103 ◽  
Author(s):  
Sho Tsujimoto ◽  
Ségolène Dessort ◽  
Naoyuki Hara ◽  
Keiji Konishi
Keyword(s):  
Wind Turbines ◽  
Pitch Angle ◽  
Offshore Wind ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines

scholarly journals Maintenance Planning of Offshore Wind Turbine Using Condition Monitoring Information

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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