GB2417498A - Windbreak - Google Patents

Abstract

The windbreak 40, for use both in commercial situations such as protecting crops and ski slopes as well as in domestic situations such as on a beach, comprises a body 62 adapted, in use, to protrude outwardly from a surface to reduce speed in a region leeward of the windbreak and which has a surface defined by one or more edges which has a wind permeability distribution wherein the wind permeability increases on average along an imaginary line drawn from the interior of the body towards one or more edges. The body may comprise a substantially planar surface and be manufactured from a sheet material such as a fabric. The body may be supported by one or more stakes 64 that may be received by sheathes provided in the body and the body may include eyelets for receiving guy ropes. The body may be modular or may be provided in sections with different central and end sections to allow for different configurations of windbreak to be set up. The wind permeability distribution may be provided by apertures 66,68,70 in the body with larger apertures being provided near to the edges of the body as compared to the interior. Alternatively the density of the apertures may be greater towards the edges of the body. The apertures may be reinforced with netting. The permeability distribution may be provided by providing differently perforated sections at different locations and the windbreak may be provided with a different permeability distribution along its intended top edge compared to its intended end edges.

Description

24 1 7498 Title: WindDreak.s

Description:

Windbreaks have been used in a variety of situations for hundreds, and perhaps thousands of years. In modern tines windbreaks are commonly in use m both domeshc situations (e.g. in the garden; on the beach), and in eornmercia] situations (e.g. for crop protection, in ski resorts, around airports, in military situations).

Windbreaks can be either artif'icia] e.g. fencing, or living e.g. a row of conifers at the edge of a field. Artificia] windbreaks such as a solid fence or wall, or a beach windbreak, suffer from problems i.e. creating turbulence in the air around them; having a very sma]] protected 'calm' zone (both in height above ground and ground f'ootpnnt area); requiting a long length to height ratio in order to ninimise edge et't'eets (typically 4(): 1 in commercial situations); in ot'f'ering such an obstruction to the wind, they are liable to be damaged or blown down, even in moderate winds; and requiring massive support structures. Living windbreaks suf'f'er fiom different ol' problems, i.e. they generally take a long time (several years) to become established; are intlexib]e and cannot be re]oeated or re-orientated; they can be]abour-intensive to establish and maintain; and are often inappropriate for sma]] situations. ..

A problem with known windbreaks is that the extent of the region of reduced.

wind speed Is sma]] relative to the surface area of the body of the windbreak. This is because the wmdUreak acts to block oncoming winds, thereby f'oreing the wind to decelerate downwardly and to accelerate upwardly, windward thereof' This causes turbulence, which tends to curl over the top of the windbreak and downwardly into the region to be protected. Turbulence can cause buffeting and in some cases, a localised wind speed increase in the lee of the windbreak.

It would be desirable to maxirnise the cahn protected zone for a windbreak of given height and length; to rmrnirnize edge effects; to rninirnise the degree of support S required for a given wind intensity; and as a consequence to rninirlJise maintenance and cost and maxrnrze flexibility to any situation where wind calming is required. It is theret'orc an object of the present invention to aim to satisfy one or more of the above requirements.

Accordingly, the present invention provides a windbreak comprising a body adapted to protrude outwardly fiom a surface for reducing the wind speed in region leeward of the windbreak; the body comprising a surface defined by one or snore edges; and the surface having a wind penneabilrty distribution; wherein the wind penneabrlity increases on average along an imaginary line drawn fiom the interior of the body towards one or more of its edges.

The present Invention may use a drt'fercntated pattern of holes set into the surface of the windbreak material (which can be any sort of flexible or inflexible material) to preserve a larninar flow patting through and around the windbreak, and minimize the boundary turbulent zone where the calm zone re-integnates with the nonnal wind pattern.

A possible advantage of the present invention is that an area of reduced wind speed extending I'or a substantial distance outside the windbreak troth vertically and horizontally n1 front of and behind the windbreak is Conned. Fur1'her possible advantages of the invention include an enlarged 'Cohn' area of greatly reduced wind speed, extending up to ten times as far behind the windbreak as the protected area provided by a solid vertical windbreak, and also extending to each side beyond the windbreak in comparison to the reduced cahn zone at the ends of a conventional windbreak - due to turbulent edge et'fects.

It is envisaged that the present invention could find domestic and commercial application - e.g. improving crop yields, improving safety on ski slopes around airports and in emergency situations, and keeping the sand out of peoples faces on the beach.

The body can take any suitable fond, although it is envisaged that providing a substantially planar surface would be a prefen-ed option. The body Nay be ] 0 manufactured of a sheet material, such as fabric, polymer, wood or metal sheet. For permanent installation, the body could be manufactured of brick or concrete.

The body can be adapted to protrude outwardly front a surface by any suitable means. In one possible embodiment of the invention, stakes are provided for driving into the ground, to which the body is affixed. The body may be affixed to the stakes, where provided, by cords, eyelets, clips etc. One or more sheathes may be ..

incorporated into the body for receiving parts of the stake or stakes. Additionally or ,., alternatively, eyelets may be provided for holding the body in-situ using guy ropes. .',, The body may be modular to facilitate installation in a variety of situations. ' ' For example, the body may be longed in sections such that it can be extended if..'4.

desired. The sections need not be the sane, i.e. the body may comprise a plurality of. . . "central" sections with "end" sections disposed at the extremities thereof.

The body comprises a surface defined by one or more edges and has a wind pemleabi]ity distribution. The wind permeability may varied by the provision of apertures or perforated sections. By distributing different sized apertures and/or differently perforated sections over the surface of tile body, the wind permeability can be configured as desired. In effect, the wind pcnneabi]ity can be adjusted by adjusting the ratio of material to aperture/perforation per unit area.

In one preferred embodiment of the Invention, apertures are disposed on the body in a pattern whereby larger apertures are provided near to the edges of the body than towards its ntcrior. The apertures, where provided, may be of any shape or size.

A variety of aperture sizes may be provided. Alternatively, the density of apertures could be increased towards the edges of the body to provide the same effect. The apertures may be reinforced using netting.

Thus, by configuring the disposition and/or size of apertures provided, the wind permeability can be arranged to increase (on average) from the interior of the body towards one or more of its edges.

A preferred embodiment of the invention shall now be described, by way of example only, with reference to the accompanying drawings, in which; Figure I shows a schematic wind flow diagram of a prior art windbreak; Figure 2 SLOWS a schematic wind flow diagram for a windbreak according to. ' . the invention; .' . Figure 3 shows a first possible embodiment of the invention; , Figures 4 to tS show alternate windbreak configurations according to the ' invention; Figure 7 shows a schematic representation of the zone of protection in plan.. '. view;

Figure S]lOWS a series of schematic plots of wind permeability versus position along imaginary lines fiom the interior to towards an edge of the invention; and Figure 9 shows an alternative embodiment of the invention having apertures of an equal size.

Referring now to Figure 1, a poor art windbreak 10 is shown arranged to protrude vertically from the grround] 2. Wind flow vectors are indicated schematically by arrows 14 to 3(). As can be seen, grround winds]4 & 16 collide with the windbreak] () and are forced to decelerate downwards. Slightly above the ground ]2, the wind is directed up and over]8, 20 & 22 the windbreak lO. Because the ground winds 14 & 16 are blocked, a region of lower pressure is created in the lee 32 of the windbreak 10. This causes the wind] 8, 20 & 22 to curl back on itself causing turbulence. Winds 24, 26, 28 & 30 higher still from the ground 12 are diverted upwards, but are nonetheless largely unaffected, thereby creating a laninar flow region 34 well above the windbreak] 0.

As can be seen, a zone of'protection created in the lee 32 of the windbreak] 0, only extends a short distance x thercbehind. The extent of the zone of protection is ] 5 typically quite sna]l, and at best, just twice the height of the windbreak, i.e. x2h.

In Figure 2, the prior art windbreak has been replaced by a windbreak according to the invention 4(). The windbreak 40 Is partially wind permeable, as shown by the fact that wind vectors 42, 44 & 46 are able to pass through therethrough.

Thus, instead of simply blocking the wind, it is partially blocked and partially slowed' which prevents a region of substantially lower pressure furor building up in the lee 60 of the windbreak 40.

Ground winds 42, 44 & 46 are theret'ore able to partially pass through the windbreak 40, WhIC]1 helps to signiticant]y reduce the amount of air turbulence generated and to bring the laminar flow region 34 closer to the grround] 2.

The windbreak 40 of the invention, by allowing a certain amount of air to pass therethrough, enables a smoother wind profile to be set up, thereby reducing turbulence and buft'eting. The net effect is to create a region of greatly reduced wind speed 60 in the lee of the windbreak, rather than a region of static air, as per the prior art. The extent of the region of'greatly reduced wind speed, however, extends much further beyond the windbreak 40, as indicated by x' than can he achieved using a similar sized prior art windbreak 40. The distance x' can be up to ten times the height of the windbreak 40, i.e. x'] Oh.

Of course, Figures 1 and 2 are idealised representations of a real situation.

] O Areas of'turbulence and/or laminar flow may, in reality, be present in either Figure, but have been omitted for clarity.

Turning now to Figure 3, a windbreak 40 according to the Invention is shown comprising a body 62 anrangcd to extend vertically from the ground. In the illustrated embodiment, the body 62 is supported by stakes 64 which are driven firmly into the ground] 2, although the body 62 can be supported in any suitable manner. The body 64 is provided with apertures 66, 68 & 70, which arc of various .

sizes. As can be seen, the largest apertures 70 are located nearest the top edges 72 of .

the body 62. Inwardly of the larger apertures 70 increasingly smaller apertures 68 & ..

66 are disposed to provide a wind permeability distribution that increases along an imaginary line y fi om towards the interior of the body 62 towards its edge 72.

Along the side edges 74 of the body 62, apertures are also provided to reduce end eflccts, which are largely the same as the turbulence caused by wind passing over the top of a conventional windbreak. The wind permeability, nonetheless increases towards the side edges 74 along imaginary line y'.

Figure 4 shows an alternative embodiment of the invention 40, whereby the body 69 is provided with areas of perforated material 76 & 78. Material 78 is more perforated than Lateral 76, thereby providing a region of greater wind penneabiLty approaching the edges 72 & 74 of the body. The perforated materials 76 & 78, in this instance, arc nets.

Figures 5 and 6 show a further alternative embodiment of the invention.

Figure 5 shows an end piece 80 and Figure 6 shows a centre piece 82 intended for use in conjunction with one another. Each piece 80 & 82 has apertures 84 disposed therein, again graduated towards the edges 72 & 74. Eyelets 86 are provided for connecting adjacent pieces 80 & 82 to one another, as well as to anchoring points (e.g. stakes or guy wires) where necessary.

Of course, it is possible to use one or more centre pieces 80 without end pieces, although end effects are likely to come into play. However, if end pieces are not required, e.g. where the windbreak 40 abuts a wall, then end pieces 82 may be ] 5 unnecessary.

F'gurc 7 shows a schematic plan view of the invention 40 vs-a-vs a prior art windbreak 10. As can be seen, the zone of protection 88 conferred by the invention fiom the prevailing wind W. is significantly larger than an equivalent sized prior art windbreak 10.

Figure 8 shows a schematic plot of wind permeability 1' as a function of distance along line y of Figure 3. As can he seen, P(y) varies step-wise. However, along a different line, e.g. line a or b, P(a) and P(b) vary differently. On average, however, P increases along an imaginary line towards an edge of the body.

Finally, Figure 9 shows an alternative embodiment of the invention 40 having apertures 70 of an equa] size. The aperture 70 spacing varies along imaginary dines p, q and r, thereby creating an increasing wind permeability variation along dine y. . . . ë e ë . e. - -

Claims (1)

1. Claims: 1. A windbreak condensing a body adapted, in use, to protrude

   outwardly from a surface for reducing the wind speed in a region leeward of the windbreak, the body comprising a surface defined by one or more edges, and the surface having a wind permeability distribution, wherein the wind permeability increases on average along an imaginary line drawn horn the interior of the body towards one or more of its edges.

   2. A windbreak as claimed in claim 1, wherein the body comprises a substantially ] O planar surface.

   3. A windbreak as claimed in claim 1 or claim 2, wherein the body is manufactured of a sheet material.

   4. A windbreak as claimed in claim 2, wherein the sheet material is fabric.

   S. A windbreak as claimed in any of claims I to 4, wherein the body is adapted to .

   I S protrude outwardly from a surface by the provision of a stake or stakes adapted to be driven into the ground, to which the body is affixed.

   6. A windbreak as claimed in claim 5, wherein one or more sheathes are provided on the body for receiving parts of the stake or stakes. 7. A windbreak as clanged in any of claims I to 6, wherein the is adapted to protrude outwardly from a surface by the provision of eyelets to which guy ropes can be attached.

   8. A windUrcak as claimed in any of claims 1 to 7, wherein the body is modular.

   9. A windbreak as claimed in chains 8, wherein the body is donned in sections.

   I (). A windbreak as claimed in claim 9, wherein different central and end sections are provided such that the windbreak can be configured for a particular situation.

   1 1. A windbreak as claimed in any of claims I to 10, wherein the wind permeability distribution is varied by the provision of apertures or perforated sections in the body.

   12. A windbreak as claimed In claim] 1, wherein the wind penneablty distribution is varied by providing different sized apertures at different locations.

   13. A windDrcak as claimed in claim] I or claim 12, wherein larger apertures are provided near to the edges of the body than towards the interior.

   14. A windbreak as claimed in any of claims 11, ]2 or 13, wherein the density of apertures is greater towards the edges of the body than towards the interior.

   ]0 15. A windbreak as claimed in any of claims I] to 14, wherein the apctures are reinforced.

   16. A windbreak as claimed in claim 15, wherein the apertures are reinforced using netting. .

   17. A windbreak as claimed in claim 1 1, wherein the wind permeability distribution is .

   varied by providing dil'f'ercntly perforated section at different locations.

   18. A windbreak as claimed in any of clangs I to 17, wherein the windbreak is . . provided with a df'ferent wind permeability distribution along its intended top edge compared to its intended end edges. .

   ]9. A windbreak substantially as hereinbef'ore described with reference to and as illustrated in Figures 2 to 9 ol'the accompanying drawings.