Nonlinear Wave Loads’ Prediction on Ultra Large Containerships

2021 ◽  
pp. 115-126
Author(s):  
Xiaoyu Li ◽  
Kaihong Zhang ◽  
Huilong Ren ◽  
Sijun Chen
Keyword(s):  
Nonlinear Wave ◽  
Wave Loads

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

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.

Nonlinear Wave Loads Acting on Cylinder Array Slowly Oscillating in Diffraction and Radiation Wave Fields

2005 ◽  
Author(s):  
Weiguang Bao ◽  
Takeshi Kinoshita ◽  
Motoki Yoshida
Keyword(s):  
Nonlinear Wave ◽  
Perturbation Expansion ◽  
Low Frequency ◽  
Added Mass ◽  
Wave Loads ◽  
Wave Fields ◽  
Wave Drift ◽  
Cylinder Array ◽  
Radiation Wave ◽  
Low Frequency Motion

The problem of a circular cylinder array slowly oscillating in both diffraction and radiation wave fields is considered in the present work. As a result of the interaction between the wave fields and the low-frequency motion, nonlinear wave loads may be separated into the so-called wave-drift added mass and damping. They are force components proportional to the square of the wave amplitude but in phase of the acceleration and velocity of the low-frequency motion respectively. The frequency of the slow oscillation is assumed to be much smaller than the wave frequency. Perturbation expansion based on two time scales and two small parameters is performed to the order to include the effects of the acceleration of the low-frequency motion. Solutions to these higher order potentials are suggested in the present work. Wave loads including the wave drift added mass and damping are evaluated by the integration of the hydrodynamic pressure over the instantaneous wetted body surface.

scholarly journals Nonlinear Wave Loads on Offshore Wind Turbines: Extreme Statistics and Fatigue

2019 ◽  
Author(s):  
Yu Zhang ◽  
Paul D. Sclavounos
Keyword(s):  
Nonlinear Wave ◽  
Wind Turbines ◽  
Offshore Wind ◽  
Wave Loads ◽  
Extreme Statistics ◽  
Support Structure ◽  
Nonlinear Load ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
The Time Domain

Abstract The development is presented of an analytical model for the prediction of the stochastic nonlinear wave loads on the support structure of bottom mounted and floating offshore wind turbines. Explicit expressions are derived for the time-domain and frequency-domain nonlinear exciting forces in a seastate with significant wave height comparable to the diameter of the support structure based on the fluid impulse theory. The higher order moments of the nonlinear load are evaluated from simulated force records and the derivation of analytical expressions for the nonlinear load statistics for their efficient use in design is addressed.

Using Nonlinear Wave Kinematics to Estimate the Loads on Offshore Wind Turbines in 3-Hour Sea States

2018 ◽  
Author(s):  
Tim Bunnik ◽  
Erik-Jan de Ridder
Keyword(s):  
Wind Turbine ◽  
Nonlinear Wave ◽  
Wind Turbines ◽  
Wave Model ◽  
Breaking Waves ◽  
Model Tests ◽  
Offshore Wind ◽  
Wave Loads ◽  
Offshore Wind Turbines ◽  
Wave Basin

The effects of operational wave loads and wind loads on offshore mono pile wind turbines are well understood. For most sites, however, the water depth is such that breaking or near-breaking waves will occur causing impulsive excitation of the mono pile and consequently considerable stresses, displacements and accelerations in the monopile, tower and turbine. As has been shown in earlier, recent publications, Computational Fluid Dynamics (CFD) can be used to accurately analyze wave impacts on offshore wind turbines. However, it is not yet well suited to study the statistical variability of wave impact loads in long-duration sea states, and thus estimate the ULS and ALS loads for which a wind turbine has to be designed. An alternative, simplified approach, is the use of a Morison model in which the kinematics (water particle velocities and accelerations) from a nonlinear wave model are used. For long-crested waves the nonlinear wave model can be run in a 2D mode and is therefore relatively cheap. In this paper model tests for steep and breaking waves on an offshore wind turbine are compared with results from the Morison model. First, a deterministic comparison is made between the wave loads from the model tests and the simulation model (simulating the same 3-hour wave realization as in the basin), which turns out to be difficult because of differences between wave reflections in the wave basin (a physical beach) and the numerical wave model (absorbing boundary condition). Second, a statistical comparison is made by comparing with different wave realizations measured in the wave basin.

A Whole Ship Finite Element Analysis With the Input of Nonlinear Wave Loads in the Irregular and Multi-Directional Waves

2011 ◽  
Author(s):  
Yoshitaka Ogawa ◽  
Masayoshi Oka
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Nonlinear Wave ◽  
Structural Strength ◽  
Wave Loads ◽  
Rational Analysis ◽  
Element Analysis ◽  
Wave Condition ◽  
Wave Pressure ◽  
Analysis System

Authors developed a whole ship finite element analysis system from a nonlinear wave loads to a structural strength at real sea state. A methodology for the rational analysis of structural strength is examined. Firstly, wave pressure, which is the input for the present whole ship finite element analysis and has much effect on the accuracy of a whole ship analysis, is validated through the comparison with experiments. It is confirmed that the present computation can estimates wave pressure in various wave condition accurately. Secondly, the whole ship finite element analysis system by the combination with the computation of nonlinear wave pressure is verified. It is verified that the present method can evaluate a structural response in irregular waves with taking account of the nonlinear effect of ship motions and slamming induced impact loads explicitly. Finally, through the structural analysis in various ship forward speed and wave condition by means of the present computation, the importance to assess a structural strength taking account of the effect of operational condition is clarified.

Probabilistic Analysis of Nonlinear Wave Loads on Ships Using Weibull, Generalized Gamma, and Pareto Distributions

2004 ◽  
Vol 48 (03) ◽  
pp. 202-217
Author(s):  
Lihua Wang ◽  
Torgeir Moan
Keyword(s):  
Nonlinear Wave ◽  
Probabilistic Analysis ◽  
Goodness Of Fit ◽  
Bending Moment ◽  
Wave Loads ◽  
Wave Load ◽  
Threshold Method ◽  
Generalized Gamma ◽  
Time Histories ◽  
Load Peak

The statistics of nonlinear wave- induced bending moment in ship hull girders in a short-term period is studied. Systematic probabilistic analysis is performed directly on wave load time histories for different ship types under various sea state and ship speed conditions. The order statistics concept and peak-over-threshold method are used for estimation of the extreme wave loads. The generalized gamma, generalized Pareto, and Weibull distributions are utilized for describing wave load peak values. The three distributions are evaluated and compared with respect to the shape parameters, goodness of fit of the models to the wave load data, and statistical uncertainty in the extreme estimates. Important features of the wave load statistics are also revealed.

Nonlinear Wave Loads Affected by the Low-Frequency Oscillations in the Horizontal Plane

2003 ◽  
Author(s):  
Takeshi Kinoshita ◽  
Weiguang Bao
Keyword(s):  
Nonlinear Wave ◽  
Perturbation Expansion ◽  
Low Frequency ◽  
Hydrodynamic Pressure ◽  
Wave Loads ◽  
Slow Oscillations ◽  
Low Frequency Oscillations ◽  
Wave Drift ◽  
Small Parameters ◽  
Wave Drift Damping

To investigate the effects of the low-frequency oscillations on the nonlinear wave loads, the interaction of the low-frequency oscillations with the ambient wave fields is considered. The frequency of the slow oscillations is assumed to be much smaller than the wave frequency. Perturbation expansion based on two small parameters, i.e. the incident wave amplitude and the low frequency, is performed to simplify the problem. Nonlinear wave loads including the wave drift damping and wave drift added mass are evaluated by the integration of the hydrodynamic pressure over the instantaneous wetted body surface. The problem is solved for a uniform circular cylinder by means of the Green’s theorem and semi-analytical solutions are presented. The far field conditions for each order of potentials are proposed to ensure the existence of a unique solution. The restriction on the validation of the solutions is discussed.

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