WO1984004767A1

WO1984004767A1 - Method and apparatus for generating a flow through a pipe below the surface of a body of water

Info

Publication number: WO1984004767A1
Application number: PCT/DK1984/000051
Authority: WO
Inventors: Ole Fjord Larsen
Original assignee: Ole Fjord Larsen
Priority date: 1983-05-31
Filing date: 1984-06-01
Publication date: 1984-12-06
Also published as: GB8314960D0; AU3015984A; EP0147441A1

Abstract

Method and apparatus for generating a flow through a contained section, e.g. a pipe, below the surface of a body of water. Fields of application include coastal protection and energy production. The contained section is connected to valved mouths located beneath different points of the migrating wave profile, whereby a uni-directional flow is induced due to the differences between the hydrostatic pressures in these points. Various configurations of the system are described, including a perforated pipe enclosed by a flexible hose, which is attached at intervals to the pipe and supplied with slits.

Description

Method and apparatus for generating a flow through a pipe below the surface of a body of water

Ohe invention relates to a method of inducing a wave-generated one-way di¬ rectional flow in a pipe below the surface of a body of water.

The flow may be utilized for various purposes, e.g. beach stabilization or energy production.

Siirple devices for rectifying a flow in a tidal area already exist. For in- stance, sewer outfalls may be supplied with flap valves allowing for flow of waste water from land toward the sea, but preventing sea water flow the opposite direction.

Under wave action, however, the outflow may be limited to the periods in which the outlet of the sewer is below the wave trough.

The present invention discloses a method and device supplied with several outlets, so that there is always an outlet beneath the wave trough, hereby inducing a constant outflow.

The invention will be described by way of examples of application and pre¬ ferred eπbodiments of the -nvention illustrated in the drawing, in which

Fig. 1 is a plan view of a coast in which the device is used for coastal protection.

Fig. 2 is an alternative cross-section , I - I, of the pipe in Fig. 1,

Fig. 3 is a schematic profile of a wave shown above a preferred eπiodiment of the invention.

Fig. 4 is a plan view of the device in Fig. 3,

Fig. 5 is a side view of a pipe with special valved mouths. Fig. 6 is a cross-section taken along the line U-II in Fig. 5.

In its simplest form the device comprises a number of pipes 2 pointing out from the same basic pipe 1, Fig. 1.

A suction for depositing the migrating beach material and thereby stabiliz¬ ing the coast may be attained through a pipe 1 parallel with or perpendicu¬ lar to the coast 6.

From this pipe 1 a number of pipes 2 extend to points at various distances from the pipe 1. Each pipe 2 is supplied with valve(s) 4 allowing for flow away from 1, but preventing flow the opposite direction.

As there will always be a mouth of one of the pipes 2 beneath the trough of a wave, the hydrostatic pressure difference will cause a constant flow out of the pipe 1, except for the moment when the trough of a wave passes over the connection point 5.

A pipe 1 for coast stabilization may for instance be a drain pipe or a rigid net enclosed by a layer of filter material, e.g. geotextile.

A pipe 1 for energy production may be solid and enclose a turbine to be driven by the induced flow through the pipe. The turbine may drive a gene¬ rator.

To prevent undermining of the pipes 1 and 2, they may have a triangular cross-section. Fig. 2. The top of the triangle may be rounded.

In stead of a plurality of pipes 2, one appropriately designed pipe 7, Figs. 3-4, may suffice.

The pipe 7 is supplied with a number of valved mouths 3, 4 along its length, or possibly one continuous valved mouth.

For the closure of the mouths beneath the wave crest and thereby establish¬ ment of hydrostatic pressure difference between the connection point 5 and the wave trough, the hydrodynamic forces of the wave may be utilized.

The mouths 3, Figs. 3-4, may be directed and formed so that the forward mo¬ tion of the water particles beneath the wave crest tend to close the valves under the crest, and so that the backward and downward motion of the water particles beneath the wave trough open up the valves under the trough.

Hereby a continuous tube between the higher hydrostatic pressure at the connection point 5 and the lowermost hydrostatic pressure at the bottom of the wave trough, and consequently a continuous flow may be established.

By adjusting the force required to open up, respectively close the valves^

a maximum flow velocity and/or -time can be obtained.

At the same time the suction caused by the backward motion in the lee of '.-. the mouths 3, 4 increases the flow velocity through the pipe 7.

To maximize this suction, protruding mouths 3, 4 like them in Figs. 3-4 therefore should have a streamlined, diminishing shape in the wave propaga¬ tion direction 8.

In cases with low wave height and/or shallow depth of water, the effect of the suction caused by the dynamic forces of the orbital wave motion may be much stronger than that of the hydrostatic pressure differences.

The valves should be of a siπple, robust design, so that their function is undisturbed by the sand in the water. Siπple flap valves may be used.

Avoόntinύous valved mouth may be made up of a drain pipe or a rigid net of plastic or metal forming the contour of the pipe, and a hose of zuτpermeable elastic sheet material attached at intervals to the inner or outer side of the pipe. The sheet being supplied with at least one longitudinal slit be¬ tween the attached cross-sections, the slit will open up, when there is an overpressure on the outer-, respectively innerside of the pipe.

Alternatively, the sheet is made of impermeable flexible or elastic material, e.g. rubber-coated textile, attached at intervals to the inner or outer side of the pipe or net. The diameter of the hose being so large, compared with the length of the periphery of the pipe, that at least one fold in the ^•• sheet is formed between the attached cross-sections, the fold is supplied with at least one longitudinal slit.

Correspondingly, slitted crosswise folds may be established.

Figs. 5-6 show still another design, in which the net 8 forming the pipe is covered with an impermeable elastic sheet 9. The sheet has overlapping sec¬ tions 10 that can be raised to the position 11 by an overpressure in the pipe, so that the water can escape.

To maximize the flow through the contained section 5, the pipe 1 may be supplied with valves allowing for flow in the same direction 12 as allowed by the valves 4.

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Claims

C L A I M S ;

1. Method of utilizing the hydrostatic pressure difference between wave crest andwave trough andor the hydronamic forces of the orbital motion of the waves to generate a flow through a contained section below the surface of a body of water, characterized by that the contained section by pipe means is connected to valved mouths located beneath different points of the wave profile.

2. Method according to Claim 1, characterized by that said valved mouths are regulated by the hydrodynamic forces of the orbital motions of the waves.

3. Apparatus for working the method according to Claim 1 or 2, characterized by that said contained section by pipe means is connected to a plurality of valved mouths spaced at different distances from the cont- tained section, as measured perpendicularly to the wave front.

4. Apparatus according to Claim 3, characterized by that said contained section is suppliedwith valve means allowing for flow in the same direction as allowed by the valved mouths of said pipe means.

5. Apparatus according to Claim 3 or 4, characterized by that said pipe means comprise a plurality of pipes, each pipe being supplied with at least one valved mouth, and the mouths being spaced at different distances from the contained section, as measured per¬ pendicularly to the wave front.

6. Apparatus according to Claim 3 or 4, characterized by that said pipe means comprise one pipe supplied with a plurality of spaced valved mouths.

7. Apparatus according to Claim 3,-4, 5 or 6, characterized by that said pipe or pipes have a triangular cross-section.

8. Apparatus according to Claim 6 or 7, characterized by that said pipe and valved mouths are made up of a drain pipe or a rigid net forming the contour of the pipe, and a hose of imperme¬ able elastic and/or flexible sheet attached at intervals to the inner or outer side of the pipe, the sheet being supplied with slits between the attached cross-sections.

9. Apparatus according to Claim 6 or 7, characterized by that said pipe and valved mouths are made up of a drain

« pipe or a rigid net forming the contour of the pipe, and a hose of iπper- meable flexible and/or elastic sheet material attached at intervals to the inner or outer side of the pipe, the hose having crosswise and/or length¬ wise overlappings or folds with expansible slits between the attached cross-sections.

10. Apparatus for working the method according to Claim 2, characterized by that said valved mouths face the approaching waves and diminishes smoothly in the wave propagation direction, or vice versa.