Nonlinear Wave Forces on Large Offshore Structures

1977 ◽  
Vol 103 (1) ◽  
pp. 166-170
Author(s):  
Michael de St.Q. Isaacson
Keyword(s):  
Nonlinear Wave ◽  
Offshore Structures ◽  
Wave Forces

A Multipole Accelerated Desingularized Method for Computing Nonlinear Wave Forces on Bodies

1998 ◽  
Vol 120 (2) ◽  
pp. 71-76 ◽  
Author(s):  
S. M. Scorpio ◽  
R. F. Beck
Keyword(s):  
Boundary Conditions ◽  
Nonlinear Wave ◽  
Mixed Boundary ◽  
Offshore Structures ◽  
Computational Effort ◽  
Boundary Integral ◽  
Boundary Integral Method ◽  
Wave Forces ◽  
Surface Boundary ◽  
Time Step

Nonlinear wave forces on offshore structures are investigated. The fluid motion is computed using a Euler-Lagrange time-domain approach. Nonlinear free surface boundary conditions are stepped forward in time using an accurate and stable integration technique. The field equation with mixed boundary conditions that result at each time step are solved at N nodes using a desingularized boundary integral method with multipole acceleration. Multipole accelerated solutions require O(N) computational effort and computer storage, while conventional solvers require O(N2) effort and storage for an iterative solution and O(N3) effort for direct inversion of the influence matrix. These methods are applied to the three-dimensional problem of wave diffraction by a vertical cylinder.

Nonlinear wave forces on a circular cylinder

1989 ◽  
Vol 16 (2) ◽  
pp. 182-187 ◽  
Author(s):  
Michael Isaacson ◽  
Qi-Hua Zuo
Keyword(s):  
Circular Cylinder ◽  
Nonlinear Wave ◽  
Perturbation Methods ◽  
Wave Force ◽  
Offshore Structures ◽  
Wave Forces ◽  
Ocean Engineering ◽  
Time Stepping ◽  
Wave Effects ◽  
Accuracy And Stability

Nonlinear wave forces on a surface-piercing vertical circular cylinder are considered using a time-stepping method previously developed which is based on Green's theorem. Possible improvements in the efficiency, accuracy, and stability of the method are considered. Results based on this method are compared with those obtained previously using perturbation methods as well as with experimental results. It is found that the time-stepping method adopted here is quite reasonable. Wave force coefficients are given as functions of the governing parameters of the problem and the importance of nonlinear wave effects on the forces is assessed. Key words: hydrodynamics, ocean engineering, offshore structures, waves, wave forces.

A Theoretical Study on the Second-Order Wave Forces for Two-Dimensional Bodies

1989 ◽  
Vol 111 (1) ◽  
pp. 37-42 ◽  
Author(s):  
G. P. Miao ◽  
Y. Z. Liu
Keyword(s):  
Nonlinear Wave ◽  
Incident Wave ◽  
Theoretical Study ◽  
Nonlinear Effects ◽  
Offshore Structures ◽  
Second Order ◽  
Wave Forces ◽  
Two Dimensional ◽  
Regular Waves ◽  
Steady Wave

Nonlinear wave forces on fixed or floating offshore structures have attracted much attention recently. This paper deals with the nonlinear effects of regular waves on fixed two-dimensional bodies up to second-order terms. The second-order diffraction potential is solved consistently and the second-order steady wave forces and the biharmonic wave forces with frequency corresponding to the double of the incident wave frequency are obtained.

scholarly journals A theory of nonlinear wave loading on offshore structures

1981 ◽  
Vol 4 (3) ◽  
pp. 589-613 ◽  
Author(s):  
Lokenath Debnath ◽  
Matiur Rahman
Keyword(s):  
Nonlinear Wave ◽  
Vertical Cylinder ◽  
Nonlinear Effects ◽  
Diffraction Theory ◽  
Offshore Structures ◽  
The Body ◽  
Wave Number ◽  
Wave Forces ◽  
Wave Loading ◽  
Nonlinear Contribution

A theoretical study is made of the nonlinear wave loading on offshore structures using the diffraction theory of hydrodynamics. A nonlinear modification of the classical Morison equation,D≡Fℓ+FDfor estimating wave forces on offshore structures is suggested in this paper. The modified equation is found in the formD≡Fℓ+Fnℓ+FDwhereFnℓ≡Fd+Fw+Fqis the nonlinear contribution made up of the dynamic, waterline, and the quadratic forces associated with the irrotational-flow part of the wave loading on structures. The study has then been applied to calculate the linear and the nonlinear wave loadings on a large vertical cylinder partially immersed in an ocean of arbitrary uniform depth. All the linear and nonlinear forces exerting on the cylinder are determined explicitly. A comparison is made between these two kinds of forces. Special attention is given to the nonlinear wave loadings on the cylinder. It is shown that all nonlinear effects come from the interaction between the body's responses to the oncoming wave's fluctuating velocity and its fluctuating extension. It is found that the nonlinear effects are dominated by the sum of the dynamic and waterline forces. The nonlinear correction to Morison's equation increases with increasingkbwherebis the characteristic dimension of the body andkis the wave number. This prediction is shown to be contrary to that of the linear diffraction theory which predicted that the Morison coefficient decreases with increasingkb. Several interesting results and limiting cases are discussed in some detail.

Detailed Study on Breaking Wave Interactions With a Jacket Structure Based on Experimental Investigations

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Jithin Jose ◽  
Olga Podrażka ◽  
Ove Tobias Gudmestad ◽  
Witold Cieślikiewicz
Keyword(s):  
Wind Turbines ◽  
Wave Breaking ◽  
Offshore Structures ◽  
Offshore Wind ◽  
Wave Forces ◽  
Breaking Wave ◽  
Offshore Wind Turbines ◽  
Wave Parameters ◽  
Wave Slamming ◽  
Breaking Wave Forces

Wave breaking is one of the major concerns for offshore structures installed in shallow waters. Impulsive breaking wave forces sometimes govern the design of such structures, particularly in areas with a sloping sea bottom. Most of the existing offshore wind turbines were installed in shallow water regions. Among fixed-type support structures for offshore wind turbines, jacket structures have become popular in recent times as the water depth for fixed offshore wind structures increases. However, there are many uncertainties in estimating breaking wave forces on a jacket structure, as only a limited number of past studies have estimated these forces. Present study is based on the WaveSlam experiment carried out in 2013, in which a jacket structure of 1:8 scale was tested for several breaking wave conditions. The total and local wave slamming forces are obtained from the experimental measured forces, using two different filtering methods. The total wave slamming forces are filtered from the measured forces using the empirical mode decomposition (EMD) method, and local slamming forces are obtained by the frequency response function (FRF) method. From these results, the peak slamming forces and slamming coefficients on the jacket members are estimated. The breaking wave forces are found to be dependent on various breaking wave parameters such as breaking wave height, wave period, wave front asymmetry, and wave-breaking positions. These wave parameters are estimated from the wave gauge measurements taken during the experiment. The dependency of the wave slamming forces on these estimated wave parameters is also investigated.

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