Modelling of a circular-section floating breakwater

1995 ◽  
Vol 22 (4) ◽  
pp. 714-722 ◽  
Author(s):  
Michael Isaacson ◽  
Neal Whiteside ◽  
Robert Gardiner ◽  
Duncan Hay
Keyword(s):  
Three Dimensional ◽  
Circular Cross Section ◽  
Diffraction Theory ◽  
Mooring Line ◽  
Coastal Structures ◽  
Regular Waves ◽  
Rectangular Section ◽  
Circular Section ◽  
Floating Breakwater ◽  
Floating Breakwaters

The physical and numerical modelling of a circular cross-section floating breakwater subjected to normal and obliquely incident regular waves is described. The transmission coefficient, breakwater motions, and mooring line forces were measured in two- and three-dimensional laboratory tests for a range of wave conditions and breakwater parameters. The experimental results are compared with results of a numerical model based on linear two-dimensional wave diffraction theory. The performance of the breakwater is summarized and compared with that of a rectangular-section breakwater. Possible modifications to improve the breakwater's performance characteristics are considered. Key words: coastal structures, floating breakwaters, hydrodynamics, moorings, waves.

scholarly journals Parametric Comparison of Rectangular and Circular Pontoons Performance as Floating Breakwater Numerically

2018 ◽  
Vol 25 (s1) ◽  
pp. 94-103 ◽  
Author(s):  
Seyyed Mohammad Reza Tabatabaei ◽  
Hamid Zeraatgar
Keyword(s):  
Cross Sections ◽  
Computer Code ◽  
Diffraction Theory ◽  
Mooring Line ◽  
Numerical Comparison ◽  
Dimensional Parameter ◽  
Hydrodynamic Analysis ◽  
Circular Section ◽  
Floating Breakwater ◽  
Floating Breakwaters

Abstract Rectangular and circular pontoons are one of the most widely cross-sections used as floating breakwaters (FB). Although, there are several articles on comparison of behavior of rectangular and circular floating breakwaters however, the Authors try to show some details of difference between these two types where they have not been addressed before. To do so, transmission coefficient (Ct), as a measure of merit, of similar rectangular and circular sections is numerically compared. A computer code is developed for two-dimensional hydrodynamic analysis of floating breakwater based on diffraction theory in frequency domain in regular waves with any configuration of mooring line. The numerical method is the finite element method and validated by comparing with experimental and numerical results. Three types of rectangular sections are defined equivalent to circular section and a numerical comparison is made between 100 similar sections. The Ct versus wave frequency has been considered in detail and three new points called LMinF, LMaxF and LMaxCt are introduced. It has been shown that LMinF and LMaxF of circular section are greater and LMaxCt is much smaller than equivalent rectangular section. The LMaxCt of both sections are very dependent to new non-dimensional parameter B/D (Breadth/Draft). Although, rectangular sections are more common for floating breakwater, however the results of this study show that possibility of using circular sections must be also considered.

scholarly journals FLOATING BREAKWATER RESPONSE TO WAVE ACTION

1988 ◽  
Vol 1 (21) ◽  
pp. 162 ◽  
Author(s):  
Michael Isaacson ◽  
Ronald Byres
Keyword(s):  
Numerical Model ◽  
Experimental Testing ◽  
Diffraction Theory ◽  
Regular Waves ◽  
Transmission Coefficients ◽  
Floating Breakwater ◽  
Mooring Forces ◽  
Wave Drift Forces ◽  
Floating Breakwaters ◽  
Incident Waves

The present paper describes a study carried out to investigate floating breakwater behavior in waves. Components of the study include a field survey of floating breakwaters in British Columbia, Canada, the development of a numerical model of breakwater behavior and the experimental testing of a particular breakwater design. The numerical model has been developed to provide breakwater motions, transmission coefficients and mooring forces. The model combines linear diffraction theory for obliquely incident waves, a mooring analysis, the inclusion of viscous damping coefficients obtained from experimental or field data, and the inclusion of drag and wave drift forces for use in the static analysis of the moorings. The experiments were carried out with normally incident regular waves of different heights and periods. Preliminary results indicate that the numerical model should prove to be a useful tool in floating breakwater design.

Wave Attenuation Performance of Floating Breakwater Needs to be Evaluated by Using Irregular Waves

2021 ◽  
Author(s):  
Chien Ming Wang ◽  
Huu Phu Nguyen ◽  
Jeong Cheol Park ◽  
Mengmeng Han ◽  
Nagi abdussamie ◽  
...  
Keyword(s):  
Transmission Coefficient ◽  
Wave Height ◽  
Wave Attenuation ◽  
Wave Spectrum ◽  
Ocean Waves ◽  
Irregular Waves ◽  
Regular Waves ◽  
Transmission Coefficients ◽  
Floating Breakwater ◽  
Floating Breakwaters

<p>Floating breakwaters have been used to protect shorelines, marinas, very large floating structures, dockyards, fish farms, harbours and ports from harsh wave environments. A floating breakwater outperforms its bottom-founded counterpart with respect to its environmental friendliness, cost-effectiveness in relatively deep waters or soft seabed conditions, flexibility for expansion and downsizing and its mobility to be towed away. The effectiveness of a floating breakwater design is assessed by its wave attenuation performance that is measured by the wave transmission coefficient (i.e., the ratio of the transmitted wave height to the incident wave height or the ratio of the transmitted wave energy to the incident wave energy). In some current design guidelines for floating breakwaters, the transmission coefficient is estimated based on the assumption that the realistic ocean waves may be represented by regular waves that are characterized by the significant wave period and wave height of the wave spectrum. There is no doubt that the use of regular waves is simple for practicing engineers designing floating breakwaters. However, the validity and accuracy of using regular waves in the evaluation of wave attenuation performance of floating breakwaters have not been thoroughly discussed in the open literature. This study examines the wave transmission coefficients of floating breakwaters by performing hydrodynamic analysis of some large floating breakwaters in ocean waves modelled as regular waves as well as irregular waves described by a wave spectrum such as the Bretschneider spectrum. The formulation of the governing fluid motion and boundary conditions are based on classical linear hydrodynamic theory. The floating breakwater is assumed to take the shape of a long rectangular box modelled by the Mindlin thick plate theory. The finite element – boundary element method was employed to solve the fluid-structure interaction problem. By considering heave-only floating box-type breakwaters of 200m and 500m in length, it is found that the transmission coefficients obtained by using the regular wave model may be smaller (or larger) than that obtained by using the irregular wave model by up to 55% (or 40%). These significant differences in the transmission coefficient estimated by using regular and irregular waves indicate that simplifying assumption of realistic ocean waves as regular waves leads to significant over/underprediction of wave attenuation performance of floating breakwaters. Thus, when designing floating breakwaters, the ocean waves have to be treated as irregular waves modelled by a wave spectrum that best describes the wave condition at the site. This conclusion is expected to motivate a revision of design guidelines for floating breakwaters for better prediction of wave attenuation performance. Also, it is expected to affect how one carries out experiments on floating breakwaters in a wave basin to measure the wave transmission coefficients.</p>

SCRAP TYRE BREAKWATERS IN COASTAL ENGINEERING

1978 ◽  
Vol 1 (16) ◽  
pp. 132 ◽  
Author(s):  
Robert Charles McGregor ◽  
Neil Sinclair Miller
Keyword(s):  
Wave Attenuation ◽  
Coastal Engineering ◽  
Performance Criteria ◽  
Extensive Literature ◽  
Coastal Structures ◽  
Floating Breakwater ◽  
Fixed Structure ◽  
Floating Breakwaters ◽  
State Of Art ◽  
Stimulation Of

The problem of the protection of shorelines and coastal structures from wave action is one of long standing. More recently it has become necessary to examine the feasibility of providing the same sort of wave attenuation for locations further offshore. Where the need for protection is in shallow water, close to the shoreline, bed-based breakwaters are possible and floating breakwaters may only be desirable on the basis of one or more of the following grounds: a) cost, b) requirement for protection being of short duration, c) reduced interference with currents, d) adaptability to changing performance criteria, e) poor foundations. As the water depth becomes larger, the costs of a fixed structure become prohibitive whereas only the anchoring fraction escalates for a floating breakwater. There is an extensive literature extending from 1842 on the floating breakwater concept. Most of the references, however, are postwar following the wartime stimulation of interest in aid of assault landings. Recent sources of state-of-art information are Kowalski (1974) and Adee (1976). The use of scrap automobile tires has been discussed by Candle (1974), Kowalski (1974, 1976) , Noble (1976) and Harms (1978). Candle was proposing what may be called near rigid mats of tires where neighbouring tyres move relatively little with respect to one another, whereas the Noble, Harms and Kowalski designs use the breakwater flexibility. In the Kowalski breakwater**, the tires are formed into groups which are known as modules which allow the breakwater to "breathe" and so dissipate more energy by internal movement as well as making construction easier. Several breakwaters of a fairly simple form have been built using this concept. These have been operational in the U.S.A. for several years and have successfully protected at least one marina through hurricane conditions.

Resonant Gas Oscillations in a Linear Area Variation Cavity: Rectangular Versus Circular Cross Section

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Sonu K. Thomas ◽  
T. M. Muruganandam
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Second Harmonic ◽  
Circular Cross Section ◽  
High Amplitude ◽  
Rectangular Section ◽  
Closed Cavity ◽  
Circular Section ◽  
Resonance Frequencies ◽  
Area Variation

Resonant gas oscillations in a linear area variation closed cavity are investigated, for two duct cross sections: rectangular and circular. The resonance frequencies were similar for both the ducts. Increased drive amplitude produced higher distortions in the waveform. It was found that both resonators exhibited commensurate behavior. This is opposed to noncommensurate behavior observed in nonuniform circular cross section resonators. The rectangular section duct had higher energy than circular section duct, in second harmonic for the same drive amplitude. The results reveal that in order to achieve shockless high amplitude pressure oscillations in a duct, both nonuniform area variation and circular cross section are required.

An Experimental Study of Effects of Water Depth on Wave Scattering and Motion Responses of a Moored Floating Breakwater in Regular Waves

2011 ◽  
Author(s):  
Zhenhua Huang ◽  
Wenbin Zhang
Keyword(s):  
Water Depth ◽  
Measurement Unit ◽  
Regular Waves ◽  
Reflection And Transmission ◽  
Transmission Coefficients ◽  
Wave Flume ◽  
Motion Responses ◽  
Floating Breakwater ◽  
Series Of Experiments ◽  
Floating Breakwaters

Due to the mobility and low costs, floating breakwaters have been frequently considered as alternatives for protecting marinas and harbors from wave attacks. Main advantages of using floating breakwaters include (i) the exchange of water between a harbor and ocean, and (ii) an adjustable elevation varying with tidal levels. When floating breakwaters are used in shallow water environments (during low tides), the presence of seabed may affect the dynamics of the floating breakwaters. In the present study, a series of experiments were carried out in a wave flume of 1.5m wide and 45m long to study the effects of water depth on the performance of a moored floating breakwater. An inertial measurement unit mounted on the breakwater measures the motion responses. The wave reflection and transmission coefficients and the responses of the breakwater to regular waves are presented for four difference water depths.

SAF file: It's really three dimensional file

2018 ◽  
Vol 14 (1) ◽  
pp. 1
Author(s):  
Prof. Dr. Jamal Aziz Mehdi
Keyword(s):  
Cross Section ◽  
Root Canal ◽  
Three Dimensional ◽  
Circular Cross Section ◽  
Circular Motion ◽  
Root Canal Treatment ◽  
Metal Core ◽  
Rotating Blade

The biological objectives of root canal treatment have not changed over the recentdecades, but the methods to attain these goals have been greatly modified. Theintroduction of NiTi rotary files represents a major leap in the development ofendodontic instruments, with a wide variety of sophisticated instruments presentlyavailable (1, 2).Whatever their modification or improvement, all of these instruments have onething in common: they consist of a metal core with some type of rotating blade thatmachines the canal with a circular motion using flutes to carry the dentin chips anddebris coronally. Consequently, all rotary NiTi files will machine the root canal to acylindrical bore with a circular cross-section if the clinician applies them in a strictboring manner

scholarly journals Representative Transmission Coefficient for Evaluating the Wave Attenuation Performance of 3D Floating Breakwaters in Regular and Irregular Waves

2021 ◽  
Vol 9 (4) ◽  
pp. 388
Author(s):  
Huu Phu Nguyen ◽  
Jeong Cheol Park ◽  
Mengmeng Han ◽  
Chien Ming Wang ◽  
Nagi Abdussamie ◽  
...  
Keyword(s):  
Transmission Coefficient ◽  
Wave Height ◽  
Wave Attenuation ◽  
Transmitted Wave ◽  
Irregular Waves ◽  
Hydrodynamic Analysis ◽  
Evaluation Approach ◽  
Floating Breakwater ◽  
Floating Breakwaters ◽  
Evaluation Approaches

Wave attenuation performance is the prime consideration when designing any floating breakwater. For a 2D hydrodynamic analysis of a floating breakwater, the wave attenuation performance is evaluated by the transmission coefficient, which is defined as the ratio between the transmitted wave height and the incident wave height. For a 3D breakwater, some researchers still adopted this evaluation approach with the transmitted wave height taken at a surface point, while others used the mean transmission coefficient within a surface area. This paper aims to first examine the rationality of these two evaluation approaches via verified numerical simulations of 3D heave-only floating breakwaters in regular and irregular waves. A new index—a representative transmission coefficient—is then presented for one to easily compare the wave attenuation performances of different 3D floating breakwater designs.

On the Flexural-Torsional Behavior of a Straight Elastic Beam Subject to Terminal Moments

1993 ◽  
Vol 60 (2) ◽  
pp. 498-505 ◽  
Author(s):  
Z. Tan ◽  
J. A. Witz
Keyword(s):  
Coordinate System ◽  
Cross Section ◽  
Equilibrium Equation ◽  
Three Dimensional ◽  
Circular Cross Section ◽  
Elastic Beam ◽  
Cartesian Coordinate System ◽  
Kinematic Constraints ◽  
Torsional Behavior ◽  
Cartesian Coordinate

This paper discusses the large-displacement flexural-torsional behavior of a straight elastic beam with uniform circular cross-section subject to arbitrary terminal bending and twisting moments. The beam is assumed to be free from any kinematic constraints at both ends. The equilibrium equation is solved analytically with the full expression for curvature to obtain the deformed configuration in a three-dimensional Cartesian coordinate system. The results show the influence of the terminal moments on the beam’s deflected configuration.

scholarly journals Numerical Simulation of the Coagulation Dynamics of Blood

2008 ◽  
Vol 9 (2) ◽  
pp. 83-104 ◽  
Author(s):  
T. Bodnár ◽  
A. Sequeira
Keyword(s):  
Blood Coagulation ◽  
Computational Study ◽  
Time Integration ◽  
Three Dimensional ◽  
Circular Cross Section ◽  
Clot Formation ◽  
Diffusion Reaction ◽  
Numerical Code ◽  
Injured Region ◽  
Reaction Equations

The process of platelet activation and blood coagulation is quite complex and not yet completely understood. Recently, a phenomenological meaningful model of blood coagulation and clot formation in flowing blood that extends existing models to integrate biochemical, physiological and rheological factors, has been developed. The aim of this paper is to present results from a computational study of a simplified version of this coupled fluid-biochemistry model. A generalized Newtonian model with shear-thinning viscosity has been adopted to describe the flow of blood. To simulate the biochemical changes and transport of various enzymes, proteins and platelets involved in the coagulation process, a set of coupled advection–diffusion–reaction equations is used. Three-dimensional numerical simulations are carried out for the whole model in a straight vessel with circular cross-section, using a finite volume semi-discretization in space, on structured grids, and a multistage scheme for time integration. Clot formation and growth are investigated in the vicinity of an injured region of the vessel wall. These are preliminary results aimed at showing the validation of the model and of the numerical code.

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