Probability distribution of random wave forces in weakly nonlinear random waves

2000 ◽  
Vol 27 (12) ◽  
pp. 1391-1405 ◽  
Author(s):  
Jin-Bao Song ◽  
Yong-Hong Wu ◽  
B. Wiwatanapataphee
Keyword(s):  
Probability Distribution ◽  
Random Wave ◽  
Wave Forces ◽  
Random Waves ◽  
Weakly Nonlinear ◽  
Nonlinear Random Waves

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.

Fatigue Analysis of a Jacket Structure to Linear and Weakly Nonlinear Random Waves

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Naser Shabakhty ◽  
Arash Khansari
Keyword(s):  
Dynamic Response ◽  
Engineering Practice ◽  
Linear Wave ◽  
Fe Model ◽  
Random Waves ◽  
Weakly Nonlinear ◽  
Analysis And Design ◽  
Jacket Structures ◽  
Wave Models ◽  
Nonlinear Random Waves

Jacket structures have been widely used in oil and gas industry and are increasingly becoming competitive as a support structure of wind turbines at different water depths. These types of structures usually fix in transition or shallow waters where numerous field observations and experiments have shown that water particles tend to exhibit non-Gaussian characteristics. However, current engineering practice ignores the wave nonlinearity for the analysis and design of these structures. The application of linear irregular models might result in considerable uncertainties in the obtained wave loads and consequently the dynamic response and thus it is highly questionable. Therefore, it is crucial to calculate the dynamic response of jacket structures under both linear and nonlinear wave models to investigate the validity of linear wave models in different sea states. In this paper, the finite element (FE) model of a jacket structure located in Persian Gulf (SP17 jacket) is setup and applied to perform a comparative study of the dynamic response to both linear and weakly nonlinear random waves. The fatigue life of the jacket structure is then calculated under both wave models. This paper will substantially improve the understanding of the dynamic response of jacket structures under fatigue damage.

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.

Modelling of Periodic and Random Wave Forces on Submarine Pipelines

2006 ◽  
Author(s):  
Francesco Aristodemo ◽  
Giuseppe R. Tomasicchio ◽  
Paolo Veltri
Keyword(s):  
Numerical Model ◽  
Laboratory Investigation ◽  
Time History ◽  
Hydrodynamic Forces ◽  
Random Wave ◽  
Wave Forces ◽  
Random Waves ◽  
Large Wave ◽  
Wave Flume ◽  
History Of

A numerical model for the prediction of the time variation of the flow field and the hydrodynamic forces on bottom submarine pipelines is proposed. The model is an extension for periodic and random waves of the Wake II hydrodynamic forces model (Soedigdo et al., 1999), originally proposed for sinusoidal waves. An extensive laboratory investigation has been carried out in order to calibrate the model. The numerical model is based on an analysis of the time history of the velocity field at each wave semi-cycle. A modified relationship of the wake velocity is introduced and the time history of the drag and lift hydrodynamic coefficients are obtained using a Gauss integration of the start-up function. The laboratory investigation was performed at the large wave flume of the Centro Sperimentale per Modelli Idraulici at Voltabarozzo (Padua, Italy). The tests were carried out by measuring the pressure values at 8 transducers mounted on a cylinder subjected to different periodic and random waves. The experiments refer to the range 4 ÷ 12 of the Keulegan-Carpenter number for periodic waves and to the range 4 ÷ 9 for random waves. The empirical parameters involved in the extended Wake II and in the classical Morison models were calibrated using the results of the sampled velocities and force time histories under different wave conditions. The comparisons between the experimental and numerical results indicate that the extended Wake II model allows an accurate evaluation of the peaks and of the phase shifts of the horizontal and vertical forces and is more accurate than the Morison model.

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