scholarly journals A fully dispersive fifth order nonlinear wave model. I: Theoretical part

2016 ◽  
Author(s):  
Y. Zhang ◽  
W.B. Feng ◽  
X.Q. Ji ◽  
M.M. Wang
Keyword(s):  
Nonlinear Wave ◽  
Wave Model ◽  
Theoretical Part ◽  
Fifth Order

scholarly journals Null modes effect in Rossby wave model

2004 ◽  
Vol 11 (3) ◽  
pp. 281-293
Author(s):  
V. Goncharov ◽  
V. Pavlov
Keyword(s):  
Nonlinear Wave ◽  
Rossby Wave ◽  
Wave Model ◽  
Wave Fields

Abstract. The problem of the null-modes existence and some particularities of their interaction with nonlinear vortex-wave-like structures is discussed. We show that the null-modes are fundamental elements of nonlinear wave fields. The conditions under which null-modes can manifest themselves are elucidated. The Rossby-Hasegawa-Mima (RHM) model is used for the illustration of features of null-modes-waves interactions.

Study on the Effect of Climate Change on Ship Responses Based on Nonlinear Simulations

2018 ◽  
Author(s):  
Bingjie Guo ◽  
Odin Gramstad ◽  
Erik Vanem ◽  
Elzbieta Bitner-Gregersen
Keyword(s):  
Climate Change ◽  
Nonlinear Wave ◽  
Structural Reliability ◽  
Failure Modes ◽  
Bending Moment ◽  
Nonlinear Effects ◽  
Wave Model ◽  
Higher Order ◽  
Hull Girder ◽  
Structural Rules

Hull girder ultimate strength, which governs sagging and hogging failures, is one of the most critical failure modes for a ship hull. The Structural Reliability Analysis (SRA) methodology has been used to develop Common Structural Rules (CRS) for tankers and bulk carriers. A linear model for bending moment in extreme weather with a nonlinear correction factor has been adopted in the analysis. It is difficult to conclude on the model uncertainty associated with nonlinear effects of bending moment as, until now, there are very limited studies addressing this topic. In this paper, the nonlinear effect on ship responses will be analyzed, and the potential effect of climate change on ship responses will be investigated with the improved 3D Rankine Panel method using nonlinear wave input. The nonlinear wave input is generated by the HOSM (Higher order Spectral Method) wave model incorporating higher order nonlinear effects, including nonlinear free-wave modulation as well as higher order bound harmonics. The North Atlantic past and projected future wave climates are considered.

Incorporating irregular nonlinear waves in simulation of dropped cylindrical objects

2019 ◽  
Vol 234 (1) ◽  
pp. 272-283
Author(s):  
Gong Xiang ◽  
C. Guedes Soares
Keyword(s):  
Nonlinear Wave ◽  
Mass Density ◽  
Wave Spectrum ◽  
Density Wave ◽  
Wave Model ◽  
Irregular Waves ◽  
Regular Waves ◽  
Initial Wave ◽  
Target Wave ◽  
Good Agreement

This study investigates the use of second-order irregular waves for estimating loads on dropped objects. The theory for the irregular nonlinear wave model is integrated into a motion prediction model to simulate the falling process of a dropped cylinder under irregular waves. Through frequency analysis, the simulated irregular waves are transformed into wave spectrum by fast Fourier transform and compared with the target wave spectrum. A good agreement between simulated wave spectrum and target wave spectrum indicates the validity of the irregular nonlinear wave model. The effects of cylinder mass density, wave amplitude and initial wave phase on the trajectory and terminal conditions of dropped cylindrical object are systematically investigated, and the simulated results are compared with those induced by regular waves.

Study on the Effect of Climate Change on Ship Responses Based on Nonlinear Simulations

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Bingjie Guo ◽  
Odin Gramstad ◽  
Erik Vanem ◽  
Elzbieta Bitner-Gregersen
Keyword(s):  
Climate Change ◽  
Nonlinear Wave ◽  
Structural Reliability ◽  
Failure Modes ◽  
Bending Moment ◽  
Nonlinear Effects ◽  
Wave Model ◽  
Higher Order ◽  
Hull Girder ◽  
Structural Rules

Hull girder ultimate strength governs sagging and hogging failures, which is one of the most critical failure modes for a ship hull. The structural reliability analysis methodology has been used to develop common structural rules for tankers and bulk carriers. A linear model for bending moment in extreme weather with a nonlinear correction factor has been adopted in the analysis. It is difficult to conclude on the model uncertainty associated with nonlinear effects of bending moment as, until now, there are few studies addressing this topic. In this paper, the nonlinear effect on ship responses is analyzed, and the potential effect of climate change on ship responses is investigated with the improved three-dimensional (3D) Rankine Panel method using nonlinear wave input. The nonlinear wave input is generated by the higher-order spectral method (HOSM) wave model incorporating higher-order nonlinear effects, including nonlinear free-wave modulation as well as higher-order bound harmonics. The past and projected future wave climates of selected locations in the North Atlantic and North Norwegian Sea are considered.

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.

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