Submerged Floating Breakwaters

In this paper we show how a submerged body can, if properly tuned to the incoming waves, reflect an appreciable amount of the incident wave energy by creating waves through its own motion which effectively cancel the incident waves passing over it. A general theory for this phenomenon is described which is applied to the cases of a hinged vertical plate and a submerged tethered horizontal circular cylinder.

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Laminar and Turbulent Free Convection From Elliptic Cylinders, With a Vertical Plate and Horizontal Circular Cylinder as Special Cases

Journal of Heat Transfer ◽

10.1115/1.3450473 ◽

1976 ◽

Vol 98 (1) ◽

pp. 72-80 ◽

Cited By ~ 68

Author(s):

G. D. Raithby ◽

K. G. T. Hollands

Keyword(s):

Heat Transfer ◽

Circular Cylinder ◽

Free Convection ◽

Vertical Plate ◽

Constant Heat Flux ◽

Special Cases ◽

Flux Boundary Conditions ◽

Large Eccentricity ◽

Rayleigh Numbers ◽

Horizontal Circular Cylinder

Heat transfer by free convection from thin elliptic cylinders is predicted, accounting for both the effect of thick boundary layers at low Rayleigh numbers and the influence of turbulence at higher Rayleigh numbers. Isothermal and constant heat flux boundary conditions are treated. The results are compared with experimental data, which are available for the limiting cases of large eccentricity (vertical plate) and small eccentricity (horizontal circular cylinder); the agreement is excellent. Accurate correlation equations, from which the average heat transfer can be calculated, are given.

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Do longshore bars shelter the shore?

Journal of Fluid Mechanics ◽

10.1017/s0022112099007168 ◽

2000 ◽

Vol 404 ◽

pp. 251-268 ◽

Cited By ~ 34

Author(s):

JIE YU ◽

CHIANG C. MEI

Keyword(s):

Spatial Distribution ◽

Incident Wave ◽

Wave Energy ◽

Phase Relation ◽

Bragg Reflection ◽

Qualitative Change ◽

Numerical Calculations ◽

Reflected Waves ◽

Incident Waves ◽

Incident Wave Energy

In most past theories on Bragg reflection of waves by a finite patch of rigid bars, only outgoing waves are allowed on the transmission side, simulating the effect of an idealized shoreline where all the incident wave energy is consumed by breaking. In these theories the amplitudes of both the incident and reflected waves are found to decrease monotonically over the bar patch in the shoreward direction. This result has motivated the idea of artificially constructing bars to protect a beach from incident waves. However, some numerical calculations have suggested that this tendency does not always hold when there is some reflection from the shore. We show here that with finite reflection by the shoreline the spatial distribution of wave energy over the patch can indeed be reversed, indicating that the mechanism can increase the hazards to the beach. The phase relation between the bars and the shoreline reflection is found to be the key to this qualitative change of wave response.

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FLOATING BREAKWATERS

Coastal Engineering Proceedings ◽

10.9753/icce.v11.68 ◽

1968 ◽

Vol 1 (11) ◽

pp. 68 ◽

Cited By ~ 5

Author(s):

A. Brebner ◽

A.O. Ofuya

Keyword(s):

Incident Wave ◽

Wave Attenuation ◽

Large Mass ◽

Radius Of Gyration ◽

Transmission Coefficients ◽

Wave Channel ◽

Mooring Forces ◽

Motion Characteristics ◽

Floating Breakwaters ◽

Incident Waves

The general objective of this investigation is to determine the wave damping characteristics of model floating breakwaters designed to reduce incident wave heights by processes of wave reflection, wave interference, forced instability of incident waves and turbulence action. Of most interest is the attempt to determine the method and the extent to which the requirement of large mass may be usefully replaced by large moment of inertia of mass in the development of floating breakwaters. Experiments are conducted in a two-dimensional wave channel. Reflection coefficients, transmission coefficients, breakwater motions and mooring forces are determined by experiments. It is found that the range of effectiveness in wave attenuation of floating breakwaters depends on several factors including breakwater design, incident wave properties, depth of water and the motion characteristics of the structures, it is remarkable that the 'A' Frame Breakwater exemplifies that the range of effectiveness of a floating breakwater can be increased by a large increase of its radius of gyration involving only a slight increase of its mass. The mooring forces are of reasonable magnitude. Experimental measurements and observations indicate that the 'A' Frame Breakwater is stable throughout the range of model tests.

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