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

2013 ◽  
Vol 135 (1) ◽  
Author(s):  
Dag Myrhaug ◽  
Muk Chen Ong
Keyword(s):  
Order Theory ◽  
Offshore Wind ◽  
Wave Crest ◽  
Random Wave ◽  
Scour Depth ◽  
Height Distribution ◽  
Random Waves ◽  
Equilibrium Scour Depth ◽  
Nonlinear Random Waves ◽  
Wave Induced

This paper provides a practical stochastic method by which the maximum equilibrium 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 wave crest height distribution (Forristall, 2000, “Wave Crest Distributions: Observations and Second-Order Theory,” J. Phys. Oceanogr., 30, pp. 1931–1943) representing both 2D and 3D nonlinear random waves, and using the regular wave formulas for scour depth by Sumer et al. (1992, “Scour Around Vertical Pile in Waves,” J. Waterway, Port, Coastal, Ocean Eng., 114(5), pp. 599–641). An example calculation is provided. Tentative approaches to related random wave-induced scour cases are also suggested.

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.

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 Time Scale for Scour Beneath Pipelines Due to Long-Crested and Short-Crested Nonlinear Random Waves Plus Current

2021 ◽  
Vol 9 (2) ◽  
pp. 114
Author(s):  
Dag Myrhaug ◽  
Muk Chen Ong
Keyword(s):  
Time Scale ◽  
Current Flow ◽  
Irregular Waves ◽  
Wave Crest ◽  
Random Wave ◽  
Random Waves ◽  
Flow Conditions ◽  
Regular Waves ◽  
Nonlinear Random Waves ◽  
2D And 3D

This article derives the time scale of pipeline scour caused by 2D (long-crested) and 3D (short-crested) nonlinear irregular waves and current for wave-dominant flow. The motivation is to provide a simple engineering tool suitable to use when assessing the time scale of equilibrium pipeline scour for these flow conditions. The method assumes the random wave process to be stationary and narrow banded adopting a distribution of the wave crest height representing 2D and 3D nonlinear irregular waves and a time scale formula for regular waves plus current. The presented results cover a range of random waves plus current flow conditions for which the method is valid. Results for typical field conditions are also presented. A possible application of the outcome of this study is that, e.g., consulting engineers can use it as part of assessing the on-bottom stability of seabed pipelines.

Burial and Scour of Short Cylinders and Truncated Cones Due to Long-Crested and Short-Crested Nonlinear Random Waves Plus Currents

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Muk Chen Ong ◽  
Dag Myrhaug
Keyword(s):  
Narrow Band ◽  
Three Dimensional ◽  
Wave Crest ◽  
Height Distribution ◽  
Random Waves ◽  
Regular Waves ◽  
Nonlinear Random Waves ◽  
2D And 3D ◽  
The Waves ◽  
Crest Height

This paper provides a practical stochastic method by which the burial and scour depths of short cylinders and truncated cones exposed to long-crested (two-dimensional (2D)) and short-crested (three-dimensional (3D)) nonlinear random waves plus currents can be derived. The approach is based on assuming the waves to be a stationary narrow-band random process, adopting the Forristall second-order wave crest height distribution representing both 2D and 3D nonlinear random waves. Moreover, the formulas for the burial and the scour depths for regular waves plus currents presented by previous published work for short cylinders and truncated cones are used.

Nonlinear Crest Height Distribution in Three-Dimensional Ocean Waves

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Felice Arena ◽  
Alfredo Ascanelli
Keyword(s):  
Water Depth ◽  
Three Dimensional ◽  
Ocean Waves ◽  
Order Theory ◽  
Second Order ◽  
Wave Crest ◽  
Height Distribution ◽  
Random Waves ◽  
Weakly Nonlinear ◽  
Wave Trough

The interest and studies on nonlinear waves are increased recently for their importance in the interaction with floating and fixed bodies. It is also well-known that nonlinearities influence wave crest and wave trough distributions, both deviating from the Rayleigh law. In this paper, a theoretical crest distribution is obtained, taking into account the extension of Boccotti’s quasideterminism theory (1982, “On Ocean Waves With High Crests,” Meccanica, 17, pp. 16–19), up to the second order for the case of three-dimensional waves in finite water depth. To this purpose, the Fedele and Arena (2005, “Weakly Nonlinear Statistics of High Random Waves,” Phys. Fluids, 17(026601), pp. 1–10) distribution is generalized to three-dimensional waves on an arbitrary water depth. The comparison with Forristall’s second order model (2000, “Wave Crest Distributions: Observations and Second-Order Theory,” J. Phys. Oceanogr., 30(8), pp. 1931–1943) shows the theoretical confirmation of his conclusion: The crest distribution in deep water for long-crested and short-crested waves are very close to each other; in shallow water the crest heights in three-dimensional waves are greater than values given by the long-crested model.

Burial and Scour of Short Cylinders and Truncated Cones due to Long-Crested and Short-Crested Nonlinear Random Waves Plus Currents

2016 ◽  
Author(s):  
Muk Chen Ong ◽  
Dag Myrhaug
Keyword(s):  
Random Process ◽  
Narrow Band ◽  
Wave Crest ◽  
Height Distribution ◽  
Random Waves ◽  
Regular Waves ◽  
Nonlinear Random Waves ◽  
2D And 3D ◽  
The Waves ◽  
Crest Height

This paper provides a practical stochastic method by which the burial and scour depths of short cylinders and truncated cones exposed to long-crested (2D) and short-crested (3D) nonlinear random waves plus currents can be derived. The approach is based on assuming the waves to be a stationary narrow-band random process, adopting the Forristall [1] wave crest height distribution representing both 2D and 3D nonlinear random waves. Moreover, the formulas for the burial and the scour depths for regular waves plus currents presented by Catano-Lopera and Garcia [2, 3] for short cylinders and Catano-Lopera et al. [4] for truncated cones are used.

scholarly journals Random Wave-Induced Burial and Scour of Short Cylinders and Truncated Cones on Mild Slopes

2017 ◽  
Author(s):  
Dag Myrhaug ◽  
Muk Chen Ong
Keyword(s):  
Random Process ◽  
Narrow Band ◽  
Stochastic Approach ◽  
Random Wave ◽  
Scour Depth ◽  
Height Distribution ◽  
Regular Waves ◽  
Wave Height Distribution ◽  
Wave Induced ◽  
The Waves

A stochastic approach calculating the random wave-induced burial and scour depth of short cylinders and truncated cones on mild slopes is provided. It assumes the waves to be a stationary narrow-band random process and a wave height distribution for mild slopes is adopted, also using formulae for the burial and scour depths for regular waves on horizontal beds for short cylinders and for truncated cones. Examples of results are also provided.

New Insights in Extreme Crest Height Distributions: A Summary of the ‘CresT’ JIP

2011 ◽  
Author(s):  
Bas Buchner ◽  
George Forristall ◽  
Kevin Ewans ◽  
Marios Christou ◽  
Janou Hennig
Keyword(s):  
Single Point ◽  
Field Measurements ◽  
Order Theory ◽  
Second Order ◽  
Wave Crest ◽  
Height Distribution ◽  
Extreme Waves ◽  
Wave Height Distribution ◽  
Floating Platforms ◽  
Crest Height

The objective of the CresT JIP was ‘to develop models for realistic extreme waves and a design methodology for the loading and response of floating platforms’. Within this objective the central question was: ‘What is the highest (most critical) wave crest that will be encountered by my platform in its lifetime?’ Based on the presented results for long and short-crested numerical, field and basin results in the paper, it can be concluded that the statistics of long-crested waves are different than those of short-crested waves. But also short-crested waves show a trend to reach crest heights above second order. This is in line with visual observations of the physics involved: crests are sharper than predicted by second order, waves are asymmetric (fronts are steeper) and waves are breaking. Although the development of extreme waves within short-crested sea states still needs further investigation (including the counteracting effect of breaking), at the end of the CresT project the following procedure for taking into account extreme waves in platform design is recommended: 1. For the wave height distribution, use the Forristall distribution (Forristall, 1978). 2. For the crest height distribution, use 2nd order distribution as basis. 3. Both the basin and field measurements show crest heights higher than predicted by second order theory for steeper sea states. It is therefore recommended to apply a correction to the second order distribution based on the basin results. 4. Account for the sampling variability at the tail of the distribution (and resulting remaining possibility of higher crests than given by the corrected second order distribution) in the reliability analysis. 5. Consider the fact that the maximum crest height under a complete platform deck can be considerably higher than the maximum crest at a single point.

scholarly journals Random wave-driven drag forces on near-bed vegetation in shallow water based on deepwater wind conditions

2019 ◽  
Vol 233 (4) ◽  
pp. 1287-1290
Author(s):  
Dag Myrhaug
Keyword(s):  
Shallow Water ◽  
Drag Force ◽  
Wind Waves ◽  
Wave Spectrum ◽  
Random Wave ◽  
Random Waves ◽  
Coastal Zones ◽  
Drag Forces ◽  
Mean Wind Speed ◽  
Wave Induced

This article provides a simple analytical method for giving estimates of random wave-driven drag forces on near-bed vegetation in shallow water from deepwater wind conditions. Results are exemplified using a Pierson–Moskowitz model wave spectrum for wind waves with the mean wind speed at the 10 m elevation above the sea surface as the parameter. The significant value of the drag force within a sea state of random waves is given, and an example typical for field conditions is presented. This method should serve as a useful tool for assessing random wave-induced drag force on vegetation in coastal zones and estuaries based on input from deepwater wind conditions.

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