A NUMERICAL STUDY OF MULTI-DIRECTIONAL IRREGULAR WAVE FIELDS AROUND COASTAL STRUCTURES

2002 ◽  
Author(s):  
TOKUZO HOSOYAMADA ◽  
SHIGERU YOSHIDA ◽  
GOZO TSUJIMOTO
Keyword(s):  
Numerical Study ◽  
Coastal Structures ◽  
Wave Fields ◽  
Irregular Wave

scholarly journals IRREGULAR WAVE OVERTOPPING RATES

1984 ◽  
Vol 1 (19) ◽  
pp. 22 ◽  
Author(s):  
Scott L. Douglass
Keyword(s):  
Shallow Water ◽  
Shore Protection ◽  
Coastal Structures ◽  
Wave Overtopping ◽  
Manual Method ◽  
Irregular Wave ◽  
Order Of Magnitude

Methods for estimating wave overtopping of coastal structures are reviewed and compared with the very limited available data and with each other. The different methods yield results which can vary more than an order-of-magnitude. For vertical seawalls, the U. S. Army Engineer Shore Protection Manual method estimates more overtopping than Goda's method except in very shallow water. For sloped structures, the Shore Protection Manual method usually estimates less overtopping than Battjes' method and Owen's method. However, data for adequately evaluating how well these methods predict overtopping has not been published.

scholarly journals Numerical Study of a Proposed Semi-Submersible Floating Platform with Different Numbers of Offset Columns Based on the DeepCwind Prototype for Improving the Wave-Resistance Ability

2019 ◽  
Vol 9 (6) ◽  
pp. 1255
Author(s):  
Zhenqing Liu ◽  
Yicheng Fan ◽  
Wei Wang ◽  
Guowei Qian
Keyword(s):  
Wind Turbines ◽  
Numerical Study ◽  
Wind Farms ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Floating Platform ◽  
Offshore Wind Turbines ◽  
Irregular Wave ◽  
Decay Test ◽  
Floating Offshore Wind Turbines

DeepCwind semi-submersible floating offshore wind turbines have been widely examined, and in some countries this type of floating offshore wind turbine has been adopted in the construction of floating wind farms. However, the DeepCwind semi-submersible floating offshore wind turbines still experience large surge motion that limits their operational time. Therefore, in this study, a semi-submersible floating platform with different numbers of offset columns, but with the same total weight, based on the DeepCwind prototype is proposed. From the free-decay test, it was found that the number of the floating columns will affect the natural frequency of the platform. Furthermore, the regular wave test in the time domain and the irregular wave test in the frequency domain show that increasing the number of the floating columns will reduce the surge motion greatly, while the effects in the heave and pitch motions are not obvious.

Numerical Study of Air Gap Response and Wave Impact Load on a Moored Semi-Submersible Platform in Predetermined Irregular Wave Train

2010 ◽  
Author(s):  
Xiufeng Liang ◽  
Jianmin Yang ◽  
Longfei Xiao ◽  
Xin Li ◽  
Jun Li
Keyword(s):  
Impact Load ◽  
Numerical Study ◽  
Wave Train ◽  
Air Gap ◽  
Navier Stokes ◽  
Design Stage ◽  
Wave Impact ◽  
Irregular Wave ◽  
Run Up ◽  
Steep Waves

The importance of understanding air gap response and potential deck impact is well-known in the design stage of semi-submersible platform. The highly non-linear nature of wave elevation around large structures in steep waves makes it difficult to accurately predict wave field under the deck and wave run up along the columns. Present engineering tools for the prediction of air gap response generally based on simplified models. Even the models accounting for nonlinear wave diffraction is not free of uncertainties. A method adopted here couples a Navier-Stokes solver, VOF technique capturing violent free surface and DNV/Seasam predicting motions of moored semi-submersible platform. Air gap response at different locations of the hull was evaluated in predetermined irregular wave train. Wave run up was also measured by wave probes near the columns. Load cells were mounted under the deck of the platform to trace potential deck impact. The predetermined irregular wave train was simulated in a numerical wave tank and verified against physical tank results. Analysis of the air gap response, wave run up and impact loads on the semi-submersible platform were conducted.

Numerical Analysis of the Performance of Perforated Coastal Structures under Irregular Wave Conditions

2015 ◽  
Vol 315 ◽  
pp. 1159-1169
Author(s):  
Insik Chun ◽  
Hak Soo Lim ◽  
Jae Seol Shim ◽  
Kyung Soo Park
Keyword(s):  
Numerical Analysis ◽  
Coastal Structures ◽  
Irregular Wave ◽  
Wave Conditions

On the observability of finite-depth short-crested water waves

1996 ◽  
Vol 322 ◽  
pp. 1-19 ◽  
Author(s):  
M. Ioualalen ◽  
A. J. Roberts ◽  
C. Kharif
Keyword(s):  
Standing Wave ◽  
Water Waves ◽  
Numerical Study ◽  
Standing Waves ◽  
Finite Depth ◽  
Two Dimensional ◽  
Wave Fields ◽  
Progressive Waves ◽  
Wave Limit ◽  
Narrow Bands

A numerical study of the superharmonic instabilities of short-crested waves on water of finite depth is performed in order to measure their time scales. It is shown that these superharmonic instabilities can be significant-unlike the deep-water case-in parts of the parameter regime. New resonances associated with the standing wave limit are studied closely. These instabilities ‘contaminate’ most of the parameter space, excluding that near two-dimensional progressive waves; however, they are significant only near the standing wave limit. The main result is that very narrow bands of both short-crested waves ‘close’ to two-dimensional standing waves, and of well developed short-crested waves, perturbed by superharmonic instabilities, are unstable for depths shallower than approximately a non-dimensional depth d= 1; the study is performed down to depth d= 0.5 beyond which the computations do not converge sufficiently. As a corollary, the present study predicts that these very narrow sub-domains of short-crested wave fields will not be observable, although most of the short-crested wave fields will be.

scholarly journals Numerical Study on Tsunami Hazard Mitigation Using a Submerged Breakwater

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Taemin Ha ◽  
Jeseon Yoo ◽  
Sejong Han ◽  
Yong-Sik Cho
Keyword(s):  
Wave Reflection ◽  
Surf Zone ◽  
Numerical Study ◽  
Tsunami Hazard ◽  
Coastal Communities ◽  
Coastal Structures ◽  
Accurate Analysis ◽  
Submerged Breakwater ◽  
Eddy Simulation ◽  
Large Eddy

Most coastal structures have been built in surf zones to protect coastal areas. In general, the transformation of waves in the surf zone is quite complicated and numerous hazards to coastal communities may be associated with such phenomena. Therefore, the behavior of waves in the surf zone should be carefully analyzed and predicted. Furthermore, an accurate analysis of deformed waves around coastal structures is directly related to the construction of economically sound and safe coastal structures because wave height plays an important role in determining the weight and shape of a levee body or armoring material. In this study, a numerical model using a large eddy simulation is employed to predict the runup heights of nonlinear waves that passed a submerged structure in the surf zone. Reduced runup heights are also predicted, and their characteristics in terms of wave reflection, transmission, and dissipation coefficients are investigated.

scholarly journals Hydrodynamic Response of the Deep Turbine Installation-Floating Concept

2019 ◽  
Author(s):  
Jordi Serret ◽  
Tim Stratford ◽  
Philipp R. Thies ◽  
Vengatesan Venugopal ◽  
Tahsin Tezdogan
Keyword(s):  
Numerical Simulations ◽  
Numerical Study ◽  
Offshore Wind ◽  
Scale Model ◽  
Offshore Wind Turbine ◽  
Mooring Lines ◽  
Scaled Model ◽  
Irregular Wave ◽  
Floating System ◽  
Turbine Installation

Abstract Floating offshore wind turbine (FOWT) installations are progressing from the R&D stage to commercial installation projects. The prospective sites are situated in increasingly deeper water and further away from the shore. This paper presents the Deep Turbine Installation-Floating (DTI-F) concept, an innovative hybrid spar buoy-based FOWT capable of being able to raise and lower the tower and nacelle, which simplifies construction, installation, maintenance and decommissioning. The study is focused on the hydrodynamics of the moored floating system, and it is based on experimental and numerical modelling work. A 1:45 Froude scaled model of the DTI-F wind concept was tested using three different mooring configurations: i) three mooring lines, ii) four mooring lines, and iii) three mooring lines with a delta connection. Free decay and stiffness decay tests were carried out together with regular and irregular wave tests. The numerical study comprises diffraction (ANSYS AQWA) and time-domain modelling (OrcaFlex). The experimental hydrostatic and hydrodynamic results are compared with the numerical simulations based on the as-built scale model. Considering the natural frequencies results obtained for the three mooring configurations, the three lines configuration without delta connection was selected as the most suitable design. The obtained results for the three mooring lines configuration show good agreement between the experiment and numerical simulations. The presented analysis of the design concept indicates a high degree of technical feasibility.

scholarly journals Numerical Study of the Impact of Climate Change on Irregular Wave Run-up Over Reef-Fringed Coasts

2020 ◽  
Vol 34 (2) ◽  
pp. 162-171 ◽  
Author(s):  
Wei-jie Liu ◽  
Ke-qi Shao ◽  
Yue Ning ◽  
Xi-zeng Zhao
Keyword(s):  
Climate Change ◽  
Numerical Study ◽  
Impact Of Climate Change ◽  
Irregular Wave ◽  
Run Up ◽  
The Impact
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