A New Type of Breakwater Utilizing Air Compressibility

Ikeno, Masaaki; Shimoda, Naokatsu; Iwata, Koichiro

doi:10.1061/9780872626874.173

Cited by 4 publications

(9 citation statements)

References 2 publications

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“…The difference between our results and the computations from the literature may be explained by the limiting modelling assumptions taken by Ikeno et al , , who assumed that the free surface moves uniformly up and down. The peak in the curve of the transmission coefficient is explained by a resonance of the free surface, which is excited if one‐half wave fits into the chamber.…”

Section: Numerical Testscontrasting

confidence: 98%

“…The structure is assumed rigid and unmovable. Such a system was proposed by Ikeno et al as a breakwater. The length L of the structure was assumed as 680mm, the height as 340mm and the thickness as 4mm.…”

Section: Numerical Testsmentioning

confidence: 99%

“…The draught was 180mm, and the water level difference between outside and inside the air chamber was 69mm. For these dimensions, experimental and numerical results for air pressure amplitudes in the chamber as well as wave reflection and transmission coefficients are available .…”

Section: Numerical Testsmentioning

confidence: 99%

“…Comparison with experimental (markers, 'o') and computational (dashed, '‐‐') from the literature . Field results for selected wave frequencies (marked by arrows) are given in Figure .…”

Section: Numerical Testsmentioning

confidence: 99%

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Fully coupled linear modelling of incompressible free‐surface flow, compressible air and flexible structures

Tóth

2016

Numerical Meth Engineering

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SUMMARYIncompressible free-surface flow is a common assumption for the modelling of water waves. Connected with the aim to develop very large floating platforms, air chamber supported floating structures have attracted considerable research interest in the past. Such structures are carried by air entrapped in chambers formed by stiff, vertical walls. In order to model these types of structures, the interactions between surface gravity waves and compressible air must be taken into account. If the payload requirements for air chamber supported structures are low enough, the air chambers may be formed by flexible membrane cylinders. In such systems, pressure variations can lead to considerable changes in chamber volume. Therefore, the flexibility of the bounding structures must be taken into account. We present a modelling strategy to tackle the fully coupled problem of compressible gas in a flexible chamber and incompressible free-surface flow in an unbounded domain. The governing equations and boundary conditions are described and solved by the finite element method. A perfectly matched layer is used to obtain a solution for an unbounded domain. Using air chambers to support very large floating structures can significantly reduce the waveinduced forces [1]. Such air chamber systems have been initially studied under the assumptions of spatially constant pressure in chambers bounded by rigid walls [2,3]. Using a semi-analytic approach for the acoustic modes in the air chamber, Lee and Newman [4] derived a model that takes spatially varying air pressure in the rigid chamber into account. All aforementioned models rely on linearised potential theory to solve the governing Laplace equation in the water domain by means of panel methods. Deformations of the platform structure may be taken into account by the use of generalised modal coordinates [5,6].In air chamber supported platforms, the buoyancy is provided by the internal pressure in one or more chambers, which are open to the water at their lower side. The internal pressure is, therefore, proportional to the platform weight. Owning to the high payload requirement of most types of very large floating structures, like floating airports or mobile offshore bases, the air chambers in systems investigated so far [1,[5][6][7][8][9] require strong bounding walls in order to sustain the resulting high internal pressure. Therefore, the chamber walls are comparatively stiff, and the behaviour of the system is governed by the compressibility of the air in the chamber. For structures with lower payload requirements, for example, usable as offshore solar power plants, the air pressure in the supporting chambers can be just several hundred Pascal above atmospheric pressure. Therefore, it is possible to form large circular cylindrical air chambers by highly flexible membranes. In such systems, the flexibility of the bounding walls must be taken into account because air pressure variations lead to substantial changes of the chamber volume. In this paper, a mechanical model for the ...

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Section: Numerical Testscontrasting

confidence: 98%

Section: Numerical Testsmentioning

confidence: 99%

Section: Numerical Testsmentioning

confidence: 99%

“…Comparison with experimental (markers, 'o') and computational (dashed, '‐‐') from the literature . Field results for selected wave frequencies (marked by arrows) are given in Figure .…”

Section: Numerical Testsmentioning

confidence: 99%

See 2 more Smart Citations

Fully coupled linear modelling of incompressible free‐surface flow, compressible air and flexible structures

Tóth

2016

Numerical Meth Engineering

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“…In some studies, an improvement of the pontoon-type breakwater is proposed, which consists of converting the space between pontoons into an air chamber. The tuning of the air pressure within the chamber is then used to adjust the resonant period of the breakwater [14]. Another approach is to use the nozzle outlet (on top of the air chamber) in order to achieve pneumatic damping [15].…”

Section: Overview Of the Floating Breakwater Designsmentioning

confidence: 99%

Dynamic Analysis of an Array of Connected Floating Breakwaters

Ćatipović

Ćorak

Alujević

et al. 2019

JMSE

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In this paper, a model for dynamic analysis of array of floating breakwaters is developed and tested. Special attention is given to modeling connections between neighboring elements of the array. A linear three-dimensional floating multi-body formulation is used as a foundation for the presented model. An additional stiffness matrix is derived which introduces the influence of the connections onto motion of the array. The stiffness matrix is used to couple motions in vertical and horizontal planes i.e., the connections are modeled in three-dimensions. The equation of motion is solved in the frequency domain. The newly developed model is tested on an array of three connected breakwaters. The motion and the performance of the breakwater array are investigated under different significant heights and directions of the incoming waves.

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Numerical study into configuration of horizontal flanges on hydrodynamic performance of moored box-type floating breakwater

Qin

Yin

2022

Ocean Engineering

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A New Type of Breakwater Utilizing Air Compressibility

Cited by 4 publications

References 2 publications

Fully coupled linear modelling of incompressible free‐surface flow, compressible air and flexible structures

Fully coupled linear modelling of incompressible free‐surface flow, compressible air and flexible structures

Dynamic Analysis of an Array of Connected Floating Breakwaters

Numerical study into configuration of horizontal flanges on hydrodynamic performance of moored box-type floating breakwater

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