scholarly journals MODEL TESTS WITH DIRECTLY REPRODUCED NATURE WAVE TRAINS

1974 ◽  
Vol 1 (14) ◽  
pp. 20 ◽  
Author(s):  
Helge Gravesen ◽  
Ebbe Fredericksen ◽  
Jens Kirkegaard
Keyword(s):  
Wave Model ◽  
Short Wave ◽  
Model Tests ◽  
Wave Forces ◽  
Wave Direction ◽  
Incoming Wave ◽  
Irregular Wave ◽  
Wave Flume ◽  
Wave Heights ◽  
Stability Of Structures

Hydraulic model tests are still recognized as the best and in many cases the only tool, indeed, for investigations of design criteria for harbours concerning a) the effect of wave disturbance on moored ships in harbour basins and at offshore terminals, b) stability of structures and wave forces on structures. Model tests with waves have until recently usually been made with regular waves varying the wave height, wave period, wave direction for each test run. An important improvement in the model technique has been the development of irregular wave generators, capable of generating waves directly from nature wave records. The following aspects are presented below 1) A discussion on the methodology of wave model tests. 2) A method for direct reproduction of nature wave records. 3) A method for determining the incoming wave heights in a short wave flume with a reflecting structure and reflection from the wave generator paddle.

The Concept of the Optimum Alignment of Discharge Pipelines Due to the Minimization of the Wave Forces

1992 ◽  
Vol 25 (9) ◽  
pp. 211-216
Author(s):  
A. Akyarli ◽  
Y. Arisoy
Keyword(s):  
Wave Height ◽  
Wave Force ◽  
Wave Forces ◽  
Wave Direction ◽  
Incoming Wave ◽  
Pipeline Route ◽  
Optimum Alignment ◽  
The Cost ◽  
Resultant Wave

As the wave forces are the function of the wave height, period and the angle between the incoming wave direction and the axis of the discharge pipeline, the resultant wave force is directly related to the alignment of the pipeline. In this paper, a method is explained to determine an optimum pipeline route for which the resultant wave force becomes minimum and hence, the cost of the constructive measures may decrease. Also, the application of this method is submitted through a case study.

Assessing Climate Change in the North Atlantic Wave Regimes

2020 ◽  
Author(s):  
M. Bernardino ◽  
M. Gonçalves ◽  
C. Guedes Soares
Keyword(s):  
System Integration ◽  
Wave Model ◽  
Offshore Structures ◽  
Future Climate ◽  
Wave Direction ◽  
Peak Period ◽  
Significant Wave ◽  
The North ◽  
Wave Heights ◽  
Mean Wave Period

Abstract An improved understanding of the present and future marine climatology is necessary for numerous activities, such as operation of offshore structures, optimization of ship routes and the evaluation of wave energy resources. To produce global wave information, the WW3 wave model was forced with wind and ice-cover data from an RCP8.5 EC-Earth system integration for two 30-year time slices. The first covering the periods from 1980 to 2009 represents the present climate and the second, covering the periods from 2070–2099, represents the climate in the end of the 21st century. Descriptive statistics of wind and wave parameters are obtained for different 30-year time slices. Regarding wind, magnitude and direction will be used. For wave, significant wave height (of total sea and swell), mean wave period, peak period, mean wave direction and energy will be investigated. Changes from present to future climate are evaluated, regarding both mean and extreme events. Maps of the theses statistics are presented. The long-term monthly joint distribution of significant wave heights and peak periods is generated. Changes from present to future climate are assessed, comparing the statistics between time slices.

scholarly journals WAVE FORCES ON SQUARE CAISSONS

1976 ◽  
Vol 1 (15) ◽  
pp. 132 ◽  
Author(s):  
G.R. Mogridge ◽  
W.W. Jamieson
Keyword(s):  
Experimental Data ◽  
Theoretical Method ◽  
Wave Forces ◽  
Simple Method ◽  
Method Of Calculation ◽  
Wave Flume ◽  
Wide Range ◽  
Wave Heights ◽  
And Storage ◽  
Water Depths

The forces and overturning moments exerted by waves on large vertical square-section caissons have been measured in the laboratory. Each model caisson extended from the bottom of a wave flume through the water surface and was oriented either with one side perpendicular to the direction of wave propagation or turned through an angle of forty-five degrees to this position. For a given orientation, each model was tested for a range of wave heights (up to the point of breaking) for various wave periods and water depths. A digital computer was used for the acquisition, processing, plotting and storage of the experimental data. In addition to the experimental work, an approximate theoretical method is presented which allows the wave loadings on a square caisson to be estimated by means of a simple desk calculation. The experimental data shows that this simple method of calculation is reasonably accurate over a wide range of wave conditions and caisson sizes.

Hydrodynamic Performance of a Novel Free Surface Pitching Breakwater

2014 ◽  
Author(s):  
Vengatesan Venugopal ◽  
Stefan Zlatev
Keyword(s):  
Body Shape ◽  
Hydrodynamic Performance ◽  
Irregular Waves ◽  
Scale Model ◽  
Reflected Waves ◽  
Irregular Wave ◽  
Wave Flume ◽  
Floating Breakwater ◽  
Wave Heights ◽  
Transmission Ct

A new concept floating breakwater was developed and tested to evaluate its hydrodynamic performance in this paper. This innovative floating breakwater has a rocking body shape which could also be used as a wave power device. A scale model was tested in a wave flume under regular and irregular wave conditions for various combinations of wave frequencies and wave heights. The breakwater has been tested for three immersion depths of 0.05 m, 0.09 m and 0.13 m from still water level. The measured transmitted and reflected waves were used to evaluate the coefficients of transmission (CT), reflection (CR) and dissipation (CL). The results illustrated that the breakwater model performed at its best when submerged at 0.13m, as this immersion depth produced lower coefficients of transmission (CT), lower reflection coefficients (CR) and higher energy dissipation (CL) coefficients. The comparison between regular and irregular waves produced similar ranges of transmission, reflection and energy coefficients.

Stochastic Linearization of the Morison Equation Applied to an Offshore Wind Turbine

2015 ◽  
Author(s):  
Charaf Ouled Housseine ◽  
Charles Monroy ◽  
Guillaume de Hauteclocque
Keyword(s):  
Wind Turbine ◽  
Wave Field ◽  
Frequency Domain ◽  
Wave Model ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Morison Equation ◽  
Incoming Wave ◽  
Irregular Wave ◽  
Seakeeping Analysis

This paper aims at comparing different implementations of the Morison equation for seakeeping analysis in frequency domain. For more consistency, different wave models are considered and the total wave field (incoming wave, the diffracted and the radiated wave field) is included in the Morison equation. A state-of-the-art of theMorison equation and the drag force linearized forms are presented. The implementation procedure, based on an iterative frequency domain scheme, is developed for the regular and the irregular wave cases. Seakeeping analysis of an offshore wind turbine is considered as an application case. A comparison between numerical simulations and measured responses is presented. For the floater’s numerical model, skirts damping effect and hydrodynamic loads applied on cylindrical bracings are modeled using the Morison equation. The drag and inertia coefficients are considered constant for all sea states and calibrated using the experimental results. Response amplitude operators (RAOs) and short-termstatistics of motions show a good agreement between experimental and numerical results. The influence of different calculation parameters including the wave model (regular/irregular) and the wave fields (incident/total) are investigated.

scholarly journals STUDY OF STATISTICAL CHARACTERISTICS OF IRREGULAR WAVE PRESSURE ON A COMPOSITE BREAKWATER

1986 ◽  
Vol 1 (20) ◽  
pp. 131
Author(s):  
Chien-Kee Chang ◽  
Ching-Her Hwang
Keyword(s):  
Pressure Distribution ◽  
Wave Height ◽  
Wave Force ◽  
Shock Pressure ◽  
Irregular Waves ◽  
Statistical Characteristics ◽  
Wave Forces ◽  
Incoming Wave ◽  
Wave Pressure ◽  
Irregular Wave

Wave pressure is the most important external force for the design of breakwater. During recent years, there has been considerable development in the technology of vertical face breakwater; however, there is no reliable method to compute wave forces induced by irregular waves. The purpose of this study is to obtain statistical characteristics of irregular wave pressure distribution from the data of model tests. The results of this study shown that vertical face breakwater under the action of irregular waves, some waves are reflected, so that the next wave breaks a critical distance resulting in a rapidly rising shock pressure on the breakwater. On the average, the wave pressure increase with incoming wave height, but the maximum wave force does not necessarily occur for the largest wave height. It can be occurred for serval larger wave group in an appropiate phase composition. The irregular wave pressure distribution on the breakwater is quite uniform; the ratio of tested and calculated wave pressures decreases with the reduction of relative crest height of breakwater. Coda formula can predict the total horizontal force of the upper part of breakwater quite well except exetreme shock pressure occurred by non-breaking waves. Wave forces calculated by Miche-Rundgren and Nagai wave force formula are about 10% cummulated exceeding percentage of wave force obtained from model test.

Experimental Study on Interaction Between Waves and Netting: Damping Effects and Forces

2007 ◽  
Author(s):  
Pa˚l F. Lader ◽  
Atle Jensen ◽  
Johan Kristian Sveen ◽  
Arne Fredheim ◽  
Anna Olsen ◽  
...  
Keyword(s):  
Fish Farming ◽  
Open Ocean ◽  
Wave Forces ◽  
Incoming Wave ◽  
Wave Flume ◽  
Narrow Wave ◽  
Damping Effects ◽  
University Of Oslo ◽  
Open Ocean Aquaculture ◽  
Nonlinear Energy

One of the possibilities to expand sea-based fish farming is to move the aquaculture installations away from the conflicts of the coastal zone, and into more open ocean locations. However, open ocean aquaculture puts other demands on the structures than aquaculture in sheltered locations, and in this context it is necessary to understand the behaviour of the aquaculture structures as they are exposed to large sea-loads from waves and current. Flexible netting is a main part of most sea-based aquaculture structures, and in this paper the interaction between waves and netting is studied. Experiments were conducted at the narrow wave flume facility at the University of Oslo, Norway, where several different regular wave cases were run through netting with different solidity. The wave energy was measured after the wave had passed through the net and compared with the energy of an undisturbed wave to assess the wave damping properties of the net. The vertical and horizontal forces were also measured. The findings show that the damping effects of the netting are not necessarily correlated with the wave forces, indicated complex nonlinear processes contributing to the fluid-net interaction. The amount of nonlinear energy in the wave and force waveforms is also investigated, and it is shown that the nonlinear energy in the incoming wave results in an even higher level of nonlinear components in the forces experienced by the net.

An Empirical Nonlinear Model to Estimate FPSO With Extended Bilge Keel Roll Linear Equivalent Damping in Extreme Seas

2012 ◽  
Author(s):  
Allan C. de Oliveira ◽  
Antonio Carlos Fernandes
Keyword(s):  
Nonlinear Model ◽  
Wave Model ◽  
Model Tests ◽  
Roll Damping ◽  
Linear Coefficient ◽  
Platform Motion ◽  
Equivalent Damping ◽  
Irregular Wave ◽  
Safe Level ◽  
Bilge Keel

Although FPSO roll damping is well known nonlinear, most of the analysis which depends on platform motion evaluations, as riser, mooring and structural analysis are based on frequency domain approach results and transfer. Due to the nonlinearity, RAOs for roll, for instance, are dependent on FPSO motion amplitude, being different for each sea state of interest. Recent researches, however, have detected a saturation level in roll damping with extended bilge keels, which means a constant damping level for larger rolling amplitudes, where a linear coefficient (viscous based) can be used in platform motion analysis. Based in model tests where this saturation occurs, a nonlinear model was fitted to this damping data in order to predict the roll damping in extreme sea conditions. Those tests have taken into account aspects which have strong influence on viscous damping, loading conditions, hull form and bilge keel characteristics. The nonlinear model implemented could provide a safe level of damping comparing the results with extreme irregular wave model tests, becoming interesting for early design phases of such structures.

Performance Analysis of a Semicircular Free Surface Breakwater

2011 ◽  
Author(s):  
Hee Min Teh ◽  
Vengatesan Venugopal ◽  
Tom Bruce
Keyword(s):  
Free Surface ◽  
Hydrodynamic Performance ◽  
Hydrodynamic Characteristics ◽  
Wave Forces ◽  
Front Wall ◽  
Wave Flume ◽  
Horizontal Wave ◽  
Wave Heights ◽  
Significant Wave Heights ◽  
Semicircular Breakwater

In the present study, the hydrodynamic performance of a semicircular free surface breakwater (SCB) has been investigated through a systematic experimental programme. Three semicircular breakwater models were tested: one with impermeable front and rear walls; a second with perforated front wall and impermeable rear wall; and a third with perforated front and rear walls. The models were tested for three submergence depths with reference to the still water level in a wave flume under irregular seas with different significant wave heights and peak periods. The performance of the breakwaters was evaluated in the form of coefficients of transmission (CT), reflection (CR) and energy dissipation (CL). The measured wave modification in front of the structure and in the breakwater’s chamber were quantified and presented in the form of a ratio relative to the incident wave height, respectively. Also, the measured horizontal wave forces acting on the SCB were analysed and reported in a dimensionless form. Empirical equations were then developed using nonlinear multiple regression models to estimate the hydrodynamic characteristics of the SCB models.

scholarly journals HONOLULU REEF RUNWAY DIKE

1970 ◽  
Vol 1 (12) ◽  
pp. 99
Author(s):  
Robert Q. Palmer ◽  
James R. Walker
Keyword(s):  
Water Depth ◽  
Water Surface ◽  
Breaking Waves ◽  
Model Tests ◽  
Transmitted Wave ◽  
Bottom Slope ◽  
Wave Runup ◽  
Wave Flume ◽  
Economical Design ◽  
Wave Heights

Criteria for design of a wave barrier to protect the proposed Honolulu International Airport Reef Runway from breaking waves were developed in wave flume model tests Structures with tribar and quarrystone armor units placed in single and multiple layers, on homogeneous and composite slopes, were subjected to both overtopping and non-overtopping breaking waves Data on wave runup, armor unit stability, quantities of overtopping water, and transmitted wave heights were obtained using a 1 50 bottom slope, which modeled the irregular coral bathymetry seaward of the proposed structure The model to prototype scale ratios ranged from 1 5 to 1 35 Model Tests indicated that the weight of armor units placed below one-third the water depth may be three-fourths that of the units located near the water surface It was noted that the maximum wave runup was 1 8 times the water depth fronting the structure Data were obtained concerning quantities of overtopping water and transmitted wave heights over the low barriers The study augments available criteria for economical design of structures subjected to breaking waves.

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